head 1.23; access; symbols netbsd-9-5-RELEASE:1.23 netbsd-11-0-RELEASE:1.23 netbsd-11-0-RC7:1.23 netbsd-11-0-RC6:1.23 netbsd-11-0-RC5:1.23 netbsd-11-0-RC4:1.23 netbsd-11-0-RC3:1.23 netbsd-11-0-RC2:1.23 netbsd-11-0-RC1:1.23 perseant-exfatfs-base-20250801:1.23 netbsd-11:1.23.0.26 netbsd-11-base:1.23 netbsd-10-1-RELEASE:1.23 perseant-exfatfs-base-20240630:1.23 perseant-exfatfs:1.23.0.24 perseant-exfatfs-base:1.23 netbsd-8-3-RELEASE:1.23 netbsd-9-4-RELEASE:1.23 netbsd-10-0-RELEASE:1.23 netbsd-10-0-RC6:1.23 netbsd-10-0-RC5:1.23 netbsd-10-0-RC4:1.23 netbsd-10-0-RC3:1.23 netbsd-10-0-RC2:1.23 netbsd-10-0-RC1:1.23 netbsd-10:1.23.0.22 netbsd-10-base:1.23 netbsd-9-3-RELEASE:1.23 cjep_sun2x-base1:1.23 cjep_sun2x:1.23.0.20 cjep_sun2x-base:1.23 cjep_staticlib_x-base1:1.23 netbsd-9-2-RELEASE:1.23 cjep_staticlib_x:1.23.0.18 cjep_staticlib_x-base:1.23 netbsd-9-1-RELEASE:1.23 phil-wifi-20200421:1.23 phil-wifi-20200411:1.23 is-mlppp:1.23.0.16 is-mlppp-base:1.23 phil-wifi-20200406:1.23 netbsd-8-2-RELEASE:1.23 netbsd-9-0-RELEASE:1.23 netbsd-9-0-RC2:1.23 netbsd-9-0-RC1:1.23 phil-wifi-20191119:1.23 netbsd-9:1.23.0.14 netbsd-9-base:1.23 phil-wifi-20190609:1.23 netbsd-8-1-RELEASE:1.23 netbsd-8-1-RC1:1.23 pgoyette-compat-merge-20190127:1.23 pgoyette-compat-20190127:1.23 pgoyette-compat-20190118:1.23 pgoyette-compat-1226:1.23 pgoyette-compat-1126:1.23 pgoyette-compat-1020:1.23 pgoyette-compat-0930:1.23 pgoyette-compat-0906:1.23 netbsd-7-2-RELEASE:1.14.4.1 pgoyette-compat-0728:1.23 netbsd-8-0-RELEASE:1.23 phil-wifi:1.23.0.12 phil-wifi-base:1.23 pgoyette-compat-0625:1.23 netbsd-8-0-RC2:1.23 pgoyette-compat-0521:1.23 pgoyette-compat-0502:1.23 pgoyette-compat-0422:1.23 netbsd-8-0-RC1:1.23 pgoyette-compat-0415:1.23 pgoyette-compat-0407:1.23 pgoyette-compat-0330:1.23 pgoyette-compat-0322:1.23 pgoyette-compat-0315:1.23 netbsd-7-1-2-RELEASE:1.14.4.1 pgoyette-compat:1.23.0.10 pgoyette-compat-base:1.23 netbsd-7-1-1-RELEASE:1.14.4.1 matt-nb8-mediatek:1.23.0.8 matt-nb8-mediatek-base:1.23 perseant-stdc-iso10646:1.23.0.6 perseant-stdc-iso10646-base:1.23 netbsd-8:1.23.0.4 netbsd-8-base:1.23 prg-localcount2-base3:1.23 prg-localcount2-base2:1.23 prg-localcount2-base1:1.23 prg-localcount2:1.23.0.2 prg-localcount2-base:1.23 pgoyette-localcount-20170426:1.23 bouyer-socketcan-base1:1.23 pgoyette-localcount-20170320:1.23 netbsd-7-1:1.14.4.1.0.6 netbsd-7-1-RELEASE:1.14.4.1 netbsd-7-1-RC2:1.14.4.1 netbsd-7-nhusb-base-20170116:1.14.4.1 bouyer-socketcan:1.22.0.2 bouyer-socketcan-base:1.22 pgoyette-localcount-20170107:1.22 netbsd-7-1-RC1:1.14.4.1 pgoyette-localcount-20161104:1.22 netbsd-7-0-2-RELEASE:1.14.4.1 localcount-20160914:1.19 netbsd-7-nhusb:1.14.4.1.0.4 netbsd-7-nhusb-base:1.14.4.1 pgoyette-localcount-20160806:1.19 pgoyette-localcount-20160726:1.19 pgoyette-localcount:1.19.0.2 pgoyette-localcount-base:1.19 netbsd-7-0-1-RELEASE:1.14.4.1 netbsd-7-0:1.14.4.1.0.2 netbsd-7-0-RELEASE:1.14.4.1 netbsd-7-0-RC3:1.14.4.1 netbsd-7-0-RC2:1.14.4.1 netbsd-7-0-RC1:1.14.4.1 netbsd-5-2-3-RELEASE:1.8 netbsd-5-1-5-RELEASE:1.8 netbsd-6-0-6-RELEASE:1.10 netbsd-6-1-5-RELEASE:1.10 netbsd-7:1.14.0.4 netbsd-7-base:1.14 yamt-pagecache-base9:1.14 yamt-pagecache-tag8:1.10.2.1 netbsd-6-1-4-RELEASE:1.10 netbsd-6-0-5-RELEASE:1.10 tls-earlyentropy:1.14.0.2 tls-earlyentropy-base:1.14 riastradh-xf86-video-intel-2-7-1-pre-2-21-15:1.14 riastradh-drm2-base3:1.14 netbsd-6-1-3-RELEASE:1.10 netbsd-6-0-4-RELEASE:1.10 netbsd-5-2-2-RELEASE:1.8 netbsd-5-1-4-RELEASE:1.8 netbsd-6-1-2-RELEASE:1.10 netbsd-6-0-3-RELEASE:1.10 netbsd-5-2-1-RELEASE:1.8 netbsd-5-1-3-RELEASE:1.8 netbsd-6-1-1-RELEASE:1.10 riastradh-drm2-base2:1.13 riastradh-drm2-base1:1.13 riastradh-drm2:1.12.0.2 riastradh-drm2-base:1.12 netbsd-6-1:1.10.0.10 netbsd-6-0-2-RELEASE:1.10 netbsd-6-1-RELEASE:1.10 netbsd-6-1-RC4:1.10 netbsd-6-1-RC3:1.10 agc-symver:1.12.0.4 agc-symver-base:1.12 netbsd-6-1-RC2:1.10 netbsd-6-1-RC1:1.10 yamt-pagecache-base8:1.12 netbsd-5-2:1.8.0.46 netbsd-6-0-1-RELEASE:1.10 yamt-pagecache-base7:1.12 netbsd-5-2-RELEASE:1.8 netbsd-5-2-RC1:1.8 matt-nb6-plus-nbase:1.10 yamt-pagecache-base6:1.12 netbsd-6-0:1.10.0.8 netbsd-6-0-RELEASE:1.10 netbsd-6-0-RC2:1.10 tls-maxphys:1.11.0.2 tls-maxphys-base:1.14 matt-nb6-plus:1.10.0.6 matt-nb6-plus-base:1.10 netbsd-6-0-RC1:1.10 yamt-pagecache-base5:1.10 yamt-pagecache-base4:1.10 netbsd-6:1.10.0.4 netbsd-6-base:1.10 netbsd-5-1-2-RELEASE:1.8 netbsd-5-1-1-RELEASE:1.8 yamt-pagecache-base3:1.10 yamt-pagecache-base2:1.10 yamt-pagecache:1.10.0.2 yamt-pagecache-base:1.10 cherry-xenmp:1.9.0.4 cherry-xenmp-base:1.9 bouyer-quota2-nbase:1.9 bouyer-quota2:1.9.0.2 bouyer-quota2-base:1.9 matt-mips64-premerge-20101231:1.9 matt-nb5-mips64-premerge-20101231:1.8 matt-nb5-pq3:1.8.0.44 matt-nb5-pq3-base:1.8 netbsd-5-1:1.8.0.42 netbsd-5-1-RELEASE:1.8 netbsd-5-1-RC4:1.8 matt-nb5-mips64-k15:1.8 netbsd-5-1-RC3:1.8 netbsd-5-1-RC2:1.8 netbsd-5-1-RC1:1.8 netbsd-5-0-2-RELEASE:1.8 matt-nb5-mips64-premerge-20091211:1.8 matt-premerge-20091211:1.8 TZCODE2009K:1.1.1.10 matt-nb5-mips64-u2-k2-k4-k7-k8-k9:1.8 matt-nb4-mips64-k7-u2a-k9b:1.8 matt-nb5-mips64-u1-k1-k5:1.8 matt-nb5-mips64:1.8.0.40 netbsd-5-0-1-RELEASE:1.8 jym-xensuspend-nbase:1.8 netbsd-5-0:1.8.0.38 netbsd-5-0-RELEASE:1.8 netbsd-5-0-RC4:1.8 netbsd-5-0-RC3:1.8 netbsd-5-0-RC2:1.8 jym-xensuspend:1.8.0.36 jym-xensuspend-base:1.8 netbsd-5-0-RC1:1.8 christos-time_t-nbase:1.8 christos-time_t:1.8.0.34 christos-time_t-base:1.8 netbsd-5:1.8.0.32 netbsd-5-base:1.8 matt-mips64-base2:1.8 matt-mips64:1.8.0.30 mjf-devfs2:1.8.0.28 mjf-devfs2-base:1.8 netbsd-4-0-1-RELEASE:1.8 wrstuden-revivesa-base-3:1.8 wrstuden-revivesa-base-2:1.8 wrstuden-fixsa-newbase:1.8 wrstuden-revivesa-base-1:1.8 yamt-pf42-base4:1.8 yamt-pf42-base3:1.8 hpcarm-cleanup-nbase:1.8 yamt-pf42-baseX:1.8 yamt-pf42-base2:1.8 wrstuden-revivesa:1.8.0.26 wrstuden-revivesa-base:1.8 yamt-pf42:1.8.0.24 yamt-pf42-base:1.8 keiichi-mipv6:1.8.0.22 keiichi-mipv6-base:1.8 matt-armv6-nbase:1.8 matt-armv6-prevmlocking:1.8 wrstuden-fixsa-base-1:1.8 netbsd-4-0:1.8.0.20 netbsd-4-0-RELEASE:1.8 cube-autoconf:1.8.0.18 cube-autoconf-base:1.8 netbsd-4-0-RC5:1.8 netbsd-4-0-RC4:1.8 netbsd-4-0-RC3:1.8 netbsd-4-0-RC2:1.8 netbsd-4-0-RC1:1.8 matt-armv6:1.8.0.16 matt-armv6-base:1.8 matt-mips64-base:1.8 hpcarm-cleanup:1.8.0.14 hpcarm-cleanup-base:1.8 netbsd-3-1-1-RELEASE:1.8 netbsd-3-0-3-RELEASE:1.8 wrstuden-fixsa:1.8.0.12 wrstuden-fixsa-base:1.8 abandoned-netbsd-4-base:1.8 abandoned-netbsd-4:1.8.0.6 netbsd-3-1:1.8.0.8 netbsd-3-1-RELEASE:1.8 netbsd-3-0-2-RELEASE:1.8 netbsd-3-1-RC4:1.8 netbsd-3-1-RC3:1.8 netbsd-3-1-RC2:1.8 netbsd-3-1-RC1:1.8 netbsd-4:1.8.0.10 netbsd-4-base:1.8 netbsd-3-0-1-RELEASE:1.8 netbsd-3-0:1.8.0.4 netbsd-3-0-RELEASE:1.8 netbsd-3-0-RC6:1.8 netbsd-3-0-RC5:1.8 netbsd-3-0-RC4:1.8 netbsd-3-0-RC3:1.8 netbsd-3-0-RC2:1.8 netbsd-3-0-RC1:1.8 netbsd-2-0-3-RELEASE:1.7.2.1 netbsd-2-1:1.7.2.1.0.4 netbsd-2-1-RELEASE:1.7.2.1 netbsd-2-1-RC6:1.7.2.1 netbsd-2-1-RC5:1.7.2.1 netbsd-2-1-RC4:1.7.2.1 netbsd-2-1-RC3:1.7.2.1 netbsd-2-1-RC2:1.7.2.1 netbsd-2-1-RC1:1.7.2.1 netbsd-2-0-2-RELEASE:1.7.2.1 netbsd-3:1.8.0.2 netbsd-3-base:1.8 netbsd-2-0-1-RELEASE:1.7.2.1 netbsd-2:1.7.2.1.0.2 netbsd-2-base:1.7.2.1 netbsd-2-0-RELEASE:1.7.2.1 netbsd-2-0-RC5:1.7.2.1 netbsd-2-0-RC4:1.7.2.1 netbsd-2-0-RC3:1.7.2.1 netbsd-2-0-RC2:1.7.2.1 netbsd-2-0-RC1:1.7.2.1 TZCODE2004A:1.1.1.9 netbsd-2-0:1.7.0.2 netbsd-2-0-base:1.7 netbsd-1-6-PATCH002-RELEASE:1.6 netbsd-1-6-PATCH002:1.6 netbsd-1-6-PATCH002-RC4:1.6 TZCODE2003E:1.1.1.8 netbsd-1-6-PATCH002-RC3:1.6 netbsd-1-6-PATCH002-RC2:1.6 TZCODE2003D:1.1.1.7 netbsd-1-6-PATCH002-RC1:1.6 netbsd-1-6-PATCH001:1.6 netbsd-1-6-PATCH001-RELEASE:1.6 netbsd-1-6-PATCH001-RC3:1.6 netbsd-1-6-PATCH001-RC2:1.6 netbsd-1-6-PATCH001-RC1:1.6 nathanw_sa_end:1.5.2.1 nathanw_sa_before_merge:1.6 fvdl_fs64_base:1.6 nathanw_sa_base:1.6 netbsd-1-6-RELEASE:1.6 netbsd-1-6-RC3:1.6 netbsd-1-6-RC2:1.6 netbsd-1-6-RC1:1.6 netbsd-1-6:1.6.0.2 netbsd-1-6-base:1.6 netbsd-1-5-PATCH003:1.4 TZCODE2002B:1.1.1.7 netbsd-1-5-PATCH002:1.4 netbsd-1-5-PATCH001:1.4 nathanw_sa:1.5.0.2 TZCODE2000G:1.1.1.6 netbsd-1-5-RELEASE:1.4 netbsd-1-5-BETA2:1.4 netbsd-1-5-BETA:1.4 netbsd-1-4-PATCH003:1.3 netbsd-1-5-ALPHA2:1.4 netbsd-1-5:1.4.0.4 netbsd-1-5-base:1.4 minoura-xpg4dl:1.4.0.2 minoura-xpg4dl-base:1.4 netbsd-1-4-PATCH002:1.3 wrstuden-devbsize-19991221:1.4 wrstuden-devbsize:1.3.0.6 wrstuden-devbsize-base:1.4 TZCODE1999I:1.1.1.5 TZCODE1999H:1.1.1.5 comdex-fall-1999:1.3.0.4 comdex-fall-1999-base:1.3 netbsd-1-4-PATCH001:1.3 netbsd-1-4-RELEASE:1.3 netbsd-1-4:1.3.0.2 netbsd-1-4-base:1.3 TZCODE1999B:1.1.1.4 netbsd-1-3-PATCH003:1.1.1.3 netbsd-1-3-PATCH003-CANDIDATE2:1.1.1.3 netbsd-1-3-PATCH003-CANDIDATE1:1.1.1.3 netbsd-1-3-PATCH003-CANDIDATE0:1.1.1.3 TZCODE1998H:1.1.1.4 TZCODE1998F:1.1.1.4 netbsd-1-3-PATCH002:1.1.1.3 netbsd-1-3-PATCH001:1.1.1.3 TZCODE1998B:1.1.1.4 TZCODE1998A:1.1.1.4 netbsd-1-3-RELEASE:1.1.1.3 netbsd-1-3-BETA:1.1.1.3 netbsd-1-3:1.1.1.3.0.2 netbsd-1-3-base:1.1.1.3 TZCODE1997G:1.1.1.3 TZCODE1997E:1.1.1.2 netbsd-1-2-PATCH001:1.1.1.2 nsswitch:1.1.1.2.0.6 ivory_soap2:1.1.1.2.0.2 netbsd-1-2-RELEASE:1.1.1.2 TZCODE96L:1.1.1.2 netbsd-1-2-BETA:1.1.1.2 netbsd-1-2:1.1.1.2.0.4 netbsd-1-2-base:1.1.1.2 TZCODE96C:1.1.1.2 TZCODE96A:1.1.1.2 netbsd-1-1-PATCH001:1.1.1.1 netbsd-1-1-RELEASE:1.1.1.1 netbsd-1-1:1.1.1.1.0.4 netbsd-1-1-base:1.1.1.1 TZCODE95C:1.1.1.1 ivory_soap:1.1.1.1.0.2 TZCODE95B:1.1.1.1 ADO:1.1.1; locks; strict; comment @# @; 1.23 date 2017.03.11.18.23.14; author christos; state Exp; branches; next 1.22; commitid 0vM6qKON28VN4aJz; 1.22 date 2016.10.20.17.41.34; author christos; state Exp; branches 1.22.2.1; next 1.21; commitid U2eCnaulQA9wpUqz; 1.21 date 2016.10.07.15.29.42; author christos; state Exp; branches; next 1.20; commitid nMAjklYYJh4b6epz; 1.20 date 2016.09.16.17.12.06; author christos; state Exp; branches; next 1.19; commitid a1L7YhATZgmalxmz; 1.19 date 2016.03.15.15.16.01; author christos; state Exp; branches 1.19.2.1; next 1.18; commitid OT5yLZPhE550EKYy; 1.18 date 2015.08.13.11.21.18; author christos; state Exp; branches; next 1.17; commitid Xg1z99BiZjvVf6xy; 1.17 date 2015.03.24.20.01.18; author christos; state Exp; branches; next 1.16; commitid Cagaae40VdCmHTey; 1.16 date 2014.10.07.21.51.03; author christos; state Exp; branches; next 1.15; commitid lOAfDYpmckVLHjTx; 1.15 date 2014.08.15.11.04.07; author christos; state Exp; branches; next 1.14; commitid QuVwzdSSxIxnPrMx; 1.14 date 2013.09.20.19.06.54; author christos; state Exp; branches 1.14.4.1; next 1.13; commitid yVHFh0qSX0xN3d6x; 1.13 date 2013.07.17.20.13.04; author christos; state Exp; branches; next 1.12; commitid PIvxLcaOBhp1xRXw; 1.12 date 2012.10.28.17.11.33; author christos; state Exp; branches 1.12.2.1; next 1.11; 1.11 date 2012.08.09.12.38.25; author christos; state Exp; branches 1.11.2.1; next 1.10; 1.10 date 2011.09.04.10.10.26; author christos; state Exp; branches 1.10.2.1; next 1.9; 1.9 date 2009.12.31.22.49.15; author mlelstv; state Exp; branches; next 1.8; 1.8 date 2004.05.27.20.39.49; author kleink; state Exp; branches; next 1.7; 1.7 date 2003.12.20.00.12.05; author kleink; state Exp; branches 1.7.2.1; next 1.6; 1.6 date 2002.01.29.12.40.33; author kleink; state Exp; branches; next 1.5; 1.5 date 2000.12.12.15.25.41; author kleink; state Exp; branches 1.5.2.1; next 1.4; 1.4 date 99.11.10.20.32.31; author kleink; state Exp; branches; next 1.3; 1.3 date 98.01.22.07.06.57; author jtc; state Exp; branches 1.3.6.1; next 1.2; 1.2 date 98.01.09.04.11.55; author perry; state Exp; branches; next 1.1; 1.1 date 95.03.10.07.08.16; author jtc; state Exp; branches 1.1.1.1; next ; 1.22.2.1 date 2017.04.21.16.53.09; author bouyer; state Exp; branches; next ; commitid dUG7nkTKALCadqOz; 1.19.2.1 date 2016.11.04.14.48.53; author pgoyette; state Exp; branches; next 1.19.2.2; commitid 2m1JRwYmpwPkOOsz; 1.19.2.2 date 2017.03.20.06.56.58; author pgoyette; state Exp; branches; next ; commitid jjw7cAwgyKq7RfKz; 1.14.4.1 date 2015.01.25.09.11.03; author martin; state Exp; branches; next ; commitid t87jNWLmrKb8Xn7y; 1.12.2.1 date 2013.07.23.21.07.29; author riastradh; state Exp; branches; next ; commitid rochtllMBJfBDDYw; 1.11.2.1 date 2012.11.20.03.00.43; author tls; state Exp; branches; next 1.11.2.2; 1.11.2.2 date 2014.08.20.00.02.16; author tls; state Exp; branches; next ; commitid jTnpym9Qu0o4R1Nx; 1.10.2.1 date 2012.10.30.18.59.04; author yamt; state Exp; branches; next 1.10.2.2; 1.10.2.2 date 2014.05.22.11.36.54; author yamt; state Exp; branches; next ; commitid HJV5p3BoaVY5KwBx; 1.7.2.1 date 2004.06.15.22.02.07; author he; state Exp; branches; next ; 1.5.2.1 date 2002.03.08.21.36.50; author nathanw; state Exp; branches; next ; 1.3.6.1 date 99.12.27.18.29.55; author wrstuden; state Exp; branches; next ; 1.1.1.1 date 95.03.10.07.08.16; author jtc; state Exp; branches 1.1.1.1.2.1; next 1.1.1.2; 1.1.1.2 date 96.01.08.22.45.14; author jtc; state Exp; branches; next 1.1.1.3; 1.1.1.3 date 97.09.05.02.07.14; author jtc; state Exp; branches; next 1.1.1.4; 1.1.1.4 date 98.01.22.06.55.52; author jtc; state Exp; branches; next 1.1.1.5; 1.1.1.5 date 99.11.10.20.23.39; author kleink; state Exp; branches; next 1.1.1.6; 1.1.1.6 date 2000.12.12.15.21.08; author kleink; state Exp; branches; next 1.1.1.7; 1.1.1.7 date 2002.01.29.12.30.30; author kleink; state Exp; branches; next 1.1.1.8; 1.1.1.8 date 2003.12.19.23.53.06; author kleink; state Exp; branches; next 1.1.1.9; 1.1.1.9 date 2004.05.27.20.36.01; author kleink; state Exp; branches; next 1.1.1.10; 1.1.1.10 date 2009.10.25.16.20.16; author mlelstv; state Exp; branches; next ; 1.1.1.1.2.1 date 95.03.10.07.08.16; author jtc; state dead; branches; next 1.1.1.1.2.2; 1.1.1.1.2.2 date 95.03.10.07.08.17; author jtc; state Exp; branches; next ; desc @@ 1.23 log @merge 2017a @ text @Theory and pragmatics of the tz code and data ----- Outline ----- Scope of the tz database Names of time zone rules Time zone abbreviations Accuracy of the tz database Time and date functions Interface stability Calendrical issues Time and time zones on Mars ----- Scope of the tz database ----- The tz database attempts to record the history and predicted future of all computer-based clocks that track civil time. To represent this data, the world is partitioned into regions whose clocks all agree about time stamps that occur after the somewhat-arbitrary cutoff point of the POSIX Epoch (1970-01-01 00:00:00 UTC). For each such region, the database records all known clock transitions, and labels the region with a notable location. Although 1970 is a somewhat-arbitrary cutoff, there are significant challenges to moving the cutoff earlier even by a decade or two, due to the wide variety of local practices before computer timekeeping became prevalent. Clock transitions before 1970 are recorded for each such location, because most systems support time stamps before 1970 and could misbehave if data entries were omitted for pre-1970 transitions. However, the database is not designed for and does not suffice for applications requiring accurate handling of all past times everywhere, as it would take far too much effort and guesswork to record all details of pre-1970 civil timekeeping. As described below, reference source code for using the tz database is also available. The tz code is upwards compatible with POSIX, an international standard for UNIX-like systems. As of this writing, the current edition of POSIX is: The Open Group Base Specifications Issue 7 IEEE Std 1003.1-2008, 2016 Edition ----- Names of time zone rules ----- Each of the database's time zone rules has a unique name. Inexperienced users are not expected to select these names unaided. Distributors should provide documentation and/or a simple selection interface that explains the names; for one example, see the 'tzselect' program in the tz code. The Unicode Common Locale Data Repository contains data that may be useful for other selection interfaces. The time zone rule naming conventions attempt to strike a balance among the following goals: * Uniquely identify every region where clocks have agreed since 1970. This is essential for the intended use: static clocks keeping local civil time. * Indicate to experts where that region is. * Be robust in the presence of political changes. For example, names of countries are ordinarily not used, to avoid incompatibilities when countries change their name (e.g. Zaire->Congo) or when locations change countries (e.g. Hong Kong from UK colony to China). * Be portable to a wide variety of implementations. * Use a consistent naming conventions over the entire world. Names normally have the form AREA/LOCATION, where AREA is the name of a continent or ocean, and LOCATION is the name of a specific location within that region. North and South America share the same area, 'America'. Typical names are 'Africa/Cairo', 'America/New_York', and 'Pacific/Honolulu'. Here are the general rules used for choosing location names, in decreasing order of importance: Use only valid POSIX file name components (i.e., the parts of names other than '/'). Do not use the file name components '.' and '..'. Within a file name component, use only ASCII letters, '.', '-' and '_'. Do not use digits, as that might create an ambiguity with POSIX TZ strings. A file name component must not exceed 14 characters or start with '-'. E.g., prefer 'Brunei' to 'Bandar_Seri_Begawan'. Exceptions: see the discussion of legacy names below. A name must not be empty, or contain '//', or start or end with '/'. Do not use names that differ only in case. Although the reference implementation is case-sensitive, some other implementations are not, and they would mishandle names differing only in case. If one name A is an initial prefix of another name AB (ignoring case), then B must not start with '/', as a regular file cannot have the same name as a directory in POSIX. For example, 'America/New_York' precludes 'America/New_York/Bronx'. Uninhabited regions like the North Pole and Bouvet Island do not need locations, since local time is not defined there. There should typically be at least one name for each ISO 3166-1 officially assigned two-letter code for an inhabited country or territory. If all the clocks in a region have agreed since 1970, don't bother to include more than one location even if subregions' clocks disagreed before 1970. Otherwise these tables would become annoyingly large. If a name is ambiguous, use a less ambiguous alternative; e.g. many cities are named San José and Georgetown, so prefer 'Costa_Rica' to 'San_Jose' and 'Guyana' to 'Georgetown'. Keep locations compact. Use cities or small islands, not countries or regions, so that any future time zone changes do not split locations into different time zones. E.g. prefer 'Paris' to 'France', since France has had multiple time zones. Use mainstream English spelling, e.g. prefer 'Rome' to 'Roma', and prefer 'Athens' to the Greek 'Αθήνα' or the Romanized 'Athína'. The POSIX file name restrictions encourage this rule. Use the most populous among locations in a zone, e.g. prefer 'Shanghai' to 'Beijing'. Among locations with similar populations, pick the best-known location, e.g. prefer 'Rome' to 'Milan'. Use the singular form, e.g. prefer 'Canary' to 'Canaries'. Omit common suffixes like '_Islands' and '_City', unless that would lead to ambiguity. E.g. prefer 'Cayman' to 'Cayman_Islands' and 'Guatemala' to 'Guatemala_City', but prefer 'Mexico_City' to 'Mexico' because the country of Mexico has several time zones. Use '_' to represent a space. Omit '.' from abbreviations in names, e.g. prefer 'St_Helena' to 'St._Helena'. Do not change established names if they only marginally violate the above rules. For example, don't change the existing name 'Rome' to 'Milan' merely because Milan's population has grown to be somewhat greater than Rome's. If a name is changed, put its old spelling in the 'backward' file. This means old spellings will continue to work. The file 'zone1970.tab' lists geographical locations used to name time zone rules. It is intended to be an exhaustive list of names for geographic regions as described above; this is a subset of the names in the data. Although a 'zone1970.tab' location's longitude corresponds to its LMT offset with one hour for every 15 degrees east longitude, this relationship is not exact. Older versions of this package used a different naming scheme, and these older names are still supported. See the file 'backward' for most of these older names (e.g., 'US/Eastern' instead of 'America/New_York'). The other old-fashioned names still supported are 'WET', 'CET', 'MET', and 'EET' (see the file 'europe'). Older versions of this package defined legacy names that are incompatible with the first rule of location names, but which are still supported. These legacy names are mostly defined in the file 'etcetera'. Also, the file 'backward' defines the legacy names 'GMT0', 'GMT-0', 'GMT+0' and 'Canada/East-Saskatchewan', and the file 'northamerica' defines the legacy names 'EST5EDT', 'CST6CDT', 'MST7MDT', and 'PST8PDT'. Excluding 'backward' should not affect the other data. If 'backward' is excluded, excluding 'etcetera' should not affect the remaining data. ----- Time zone abbreviations ----- When this package is installed, it generates time zone abbreviations like 'EST' to be compatible with human tradition and POSIX. Here are the general rules used for choosing time zone abbreviations, in decreasing order of importance: Use three or more characters that are ASCII alphanumerics or '+' or '-'. Previous editions of this database also used characters like ' ' and '?', but these characters have a special meaning to the shell and cause commands like set `date` to have unexpected effects. Previous editions of this rule required upper-case letters, but the Congressman who introduced Chamorro Standard Time preferred "ChST", so lower-case letters are now allowed. Also, POSIX from 2001 on relaxed the rule to allow '-', '+', and alphanumeric characters from the portable character set in the current locale. In practice ASCII alphanumerics and '+' and '-' are safe in all locales. In other words, in the C locale the POSIX extended regular expression [-+[:alnum:]]{3,} should match the abbreviation. This guarantees that all abbreviations could have been specified by a POSIX TZ string. Use abbreviations that are in common use among English-speakers, e.g. 'EST' for Eastern Standard Time in North America. We assume that applications translate them to other languages as part of the normal localization process; for example, a French application might translate 'EST' to 'HNE'. For zones whose times are taken from a city's longitude, use the traditional xMT notation, e.g. 'PMT' for Paris Mean Time. The only name like this in current use is 'GMT'. Use 'LMT' for local mean time of locations before the introduction of standard time; see "Scope of the tz database". If there is no common English abbreviation, use numeric offsets like -05 and +0830 that are generated by zic's %z notation. Use current abbreviations for older timestamps to avoid confusion. For example, in 1910 a common English abbreviation for UT +01 in central Europe was 'MEZ' (short for both "Middle European Zone" and for "Mitteleuropäische Zeit" in German). Nowadays 'CET' ("Central European Time") is more common in English, and the database uses 'CET' even for circa-1910 timestamps as this is less confusing for modern users and avoids the need for determining when 'CET' supplanted 'MEZ' in common usage. Use a consistent style in a zone's history. For example, if a zone's history tends to use numeric abbreviations and a particular entry could go either way, use a numeric abbreviation. [The remaining guidelines predate the introduction of %z. They are problematic as they mean tz data entries invent notation rather than record it. These guidelines are now deprecated and the plan is to gradually move to %z for inhabited locations and to "-00" for uninhabited locations.] If there is no common English abbreviation, abbreviate the English translation of the usual phrase used by native speakers. If this is not available or is a phrase mentioning the country (e.g. "Cape Verde Time"), then: When a country is identified with a single or principal zone, append 'T' to the country's ISO code, e.g. 'CVT' for Cape Verde Time. For summer time append 'ST'; for double summer time append 'DST'; etc. Otherwise, take the first three letters of an English place name identifying each zone and append 'T', 'ST', etc. as before; e.g. 'CHAST' for CHAtham Summer Time. Use UT (with time zone abbreviation '-00') for locations while uninhabited. The leading '-' is a flag that the time zone is in some sense undefined; this notation is derived from Internet RFC 3339. Application writers should note that these abbreviations are ambiguous in practice: e.g. 'CST' has a different meaning in China than it does in the United States. In new applications, it's often better to use numeric UT offsets like '-0600' instead of time zone abbreviations like 'CST'; this avoids the ambiguity. ----- Accuracy of the tz database ----- The tz database is not authoritative, and it surely has errors. Corrections are welcome and encouraged; see the file CONTRIBUTING. Users requiring authoritative data should consult national standards bodies and the references cited in the database's comments. Errors in the tz database arise from many sources: * The tz database predicts future time stamps, and current predictions will be incorrect after future governments change the rules. For example, if today someone schedules a meeting for 13:00 next October 1, Casablanca time, and tomorrow Morocco changes its daylight saving rules, software can mess up after the rule change if it blithely relies on conversions made before the change. * The pre-1970 entries in this database cover only a tiny sliver of how clocks actually behaved; the vast majority of the necessary information was lost or never recorded. Thousands more zones would be needed if the tz database's scope were extended to cover even just the known or guessed history of standard time; for example, the current single entry for France would need to split into dozens of entries, perhaps hundreds. And in most of the world even this approach would be misleading due to widespread disagreement or indifference about what times should be observed. In her 2015 book "The Global Transformation of Time, 1870-1950", Vanessa Ogle writes "Outside of Europe and North America there was no system of time zones at all, often not even a stable landscape of mean times, prior to the middle decades of the twentieth century". See: Timothy Shenk, Booked: A Global History of Time. Dissent 2015-12-17 https://www.dissentmagazine.org/blog/booked-a-global-history-of-time-vanessa-ogle * Most of the pre-1970 data entries come from unreliable sources, often astrology books that lack citations and whose compilers evidently invented entries when the true facts were unknown, without reporting which entries were known and which were invented. These books often contradict each other or give implausible entries, and on the rare occasions when they are checked they are typically found to be incorrect. * For the UK the tz database relies on years of first-class work done by Joseph Myers and others; see . Other countries are not done nearly as well. * Sometimes, different people in the same city would maintain clocks that differed significantly. Railway time was used by railroad companies (which did not always agree with each other), church-clock time was used for birth certificates, etc. Often this was merely common practice, but sometimes it was set by law. For example, from 1891 to 1911 the UT offset in France was legally 0:09:21 outside train stations and 0:04:21 inside. * Although a named location in the tz database stands for the containing region, its pre-1970 data entries are often accurate for only a small subset of that region. For example, Europe/London stands for the United Kingdom, but its pre-1847 times are valid only for locations that have London's exact meridian, and its 1847 transition to GMT is known to be valid only for the L&NW and the Caledonian railways. * The tz database does not record the earliest time for which a zone's data entries are thereafter valid for every location in the region. For example, Europe/London is valid for all locations in its region after GMT was made the standard time, but the date of standardization (1880-08-02) is not in the tz database, other than in commentary. For many zones the earliest time of validity is unknown. * The tz database does not record a region's boundaries, and in many cases the boundaries are not known. For example, the zone America/Kentucky/Louisville represents a region around the city of Louisville, the boundaries of which are unclear. * Changes that are modeled as instantaneous transitions in the tz database were often spread out over hours, days, or even decades. * Even if the time is specified by law, locations sometimes deliberately flout the law. * Early timekeeping practices, even assuming perfect clocks, were often not specified to the accuracy that the tz database requires. * Sometimes historical timekeeping was specified more precisely than what the tz database can handle. For example, from 1909 to 1937 Netherlands clocks were legally UT +00:19:32.13, but the tz database cannot represent the fractional second. * Even when all the timestamp transitions recorded by the tz database are correct, the tz rules that generate them may not faithfully reflect the historical rules. For example, from 1922 until World War II the UK moved clocks forward the day following the third Saturday in April unless that was Easter, in which case it moved clocks forward the previous Sunday. Because the tz database has no way to specify Easter, these exceptional years are entered as separate tz Rule lines, even though the legal rules did not change. * The tz database models pre-standard time using the proleptic Gregorian calendar and local mean time (LMT), but many people used other calendars and other timescales. For example, the Roman Empire used the Julian calendar, and had 12 varying-length daytime hours with a non-hour-based system at night. * Early clocks were less reliable, and data entries do not represent clock error. * The tz database assumes Universal Time (UT) as an origin, even though UT is not standardized for older time stamps. In the tz database commentary, UT denotes a family of time standards that includes Coordinated Universal Time (UTC) along with other variants such as UT1 and GMT, with days starting at midnight. Although UT equals UTC for modern time stamps, UTC was not defined until 1960, so commentary uses the more-general abbreviation UT for time stamps that might predate 1960. Since UT, UT1, etc. disagree slightly, and since pre-1972 UTC seconds varied in length, interpretation of older time stamps can be problematic when subsecond accuracy is needed. * Civil time was not based on atomic time before 1972, and we don't know the history of earth's rotation accurately enough to map SI seconds to historical solar time to more than about one-hour accuracy. See: Stephenson FR, Morrison LV, Hohenkerk CY. Measurement of the Earth's rotation: 720 BC to AD 2015. Proc Royal Soc A. 2016 Dec 7;472:20160404. http://dx.doi.org/10.1098/rspa.2016.0404 Also see: Espenak F. Uncertainty in Delta T (ΔT). http://eclipse.gsfc.nasa.gov/SEhelp/uncertainty2004.html * The relationship between POSIX time (that is, UTC but ignoring leap seconds) and UTC is not agreed upon after 1972. Although the POSIX clock officially stops during an inserted leap second, at least one proposed standard has it jumping back a second instead; and in practice POSIX clocks more typically either progress glacially during a leap second, or are slightly slowed while near a leap second. * The tz database does not represent how uncertain its information is. Ideally it would contain information about when data entries are incomplete or dicey. Partial temporal knowledge is a field of active research, though, and it's not clear how to apply it here. In short, many, perhaps most, of the tz database's pre-1970 and future time stamps are either wrong or misleading. Any attempt to pass the tz database off as the definition of time should be unacceptable to anybody who cares about the facts. In particular, the tz database's LMT offsets should not be considered meaningful, and should not prompt creation of zones merely because two locations differ in LMT or transitioned to standard time at different dates. ----- Time and date functions ----- The tz code contains time and date functions that are upwards compatible with those of POSIX. POSIX has the following properties and limitations. * In POSIX, time display in a process is controlled by the environment variable TZ. Unfortunately, the POSIX TZ string takes a form that is hard to describe and is error-prone in practice. Also, POSIX TZ strings can't deal with other (for example, Israeli) daylight saving time rules, or situations where more than two time zone abbreviations are used in an area. The POSIX TZ string takes the following form: stdoffset[dst[offset][,date[/time],date[/time]]] where: std and dst are 3 or more characters specifying the standard and daylight saving time (DST) zone names. Starting with POSIX.1-2001, std and dst may also be in a quoted form like ""; this allows "+" and "-" in the names. offset is of the form '[+-]hh:[mm[:ss]]' and specifies the offset west of UT. 'hh' may be a single digit; 0<=hh<=24. The default DST offset is one hour ahead of standard time. date[/time],date[/time] specifies the beginning and end of DST. If this is absent, the system supplies its own rules for DST, and these can differ from year to year; typically US DST rules are used. time takes the form 'hh:[mm[:ss]]' and defaults to 02:00. This is the same format as the offset, except that a leading '+' or '-' is not allowed. date takes one of the following forms: Jn (1<=n<=365) origin-1 day number not counting February 29 n (0<=n<=365) origin-0 day number counting February 29 if present Mm.n.d (0[Sunday]<=d<=6[Saturday], 1<=n<=5, 1<=m<=12) for the dth day of week n of month m of the year, where week 1 is the first week in which day d appears, and '5' stands for the last week in which day d appears (which may be either the 4th or 5th week). Typically, this is the only useful form; the n and Jn forms are rarely used. Here is an example POSIX TZ string, for US Pacific time using rules appropriate from 1987 through 2006: TZ='PST8PDT,M4.1.0/02:00,M10.5.0/02:00' This POSIX TZ string is hard to remember, and mishandles time stamps before 1987 and after 2006. With this package you can use this instead: TZ='America/Los_Angeles' * POSIX does not define the exact meaning of TZ values like "EST5EDT". Typically the current US DST rules are used to interpret such values, but this means that the US DST rules are compiled into each program that does time conversion. This means that when US time conversion rules change (as in the United States in 1987), all programs that do time conversion must be recompiled to ensure proper results. * The TZ environment variable is process-global, which makes it hard to write efficient, thread-safe applications that need access to multiple time zones. * In POSIX, there's no tamper-proof way for a process to learn the system's best idea of local wall clock. (This is important for applications that an administrator wants used only at certain times - without regard to whether the user has fiddled the "TZ" environment variable. While an administrator can "do everything in UTC" to get around the problem, doing so is inconvenient and precludes handling daylight saving time shifts - as might be required to limit phone calls to off-peak hours.) * POSIX provides no convenient and efficient way to determine the UT offset and time zone abbreviation of arbitrary time stamps, particularly for time zone settings that do not fit into the POSIX model. * POSIX requires that systems ignore leap seconds. * The tz code attempts to support all the time_t implementations allowed by POSIX. The time_t type represents a nonnegative count of seconds since 1970-01-01 00:00:00 UTC, ignoring leap seconds. In practice, time_t is usually a signed 64- or 32-bit integer; 32-bit signed time_t values stop working after 2038-01-19 03:14:07 UTC, so new implementations these days typically use a signed 64-bit integer. Unsigned 32-bit integers are used on one or two platforms, and 36-bit and 40-bit integers are also used occasionally. Although earlier POSIX versions allowed time_t to be a floating-point type, this was not supported by any practical systems, and POSIX.1-2013 and the tz code both require time_t to be an integer type. These are the extensions that have been made to the POSIX functions: * The "TZ" environment variable is used in generating the name of a file from which time zone information is read (or is interpreted a la POSIX); "TZ" is no longer constrained to be a three-letter time zone name followed by a number of hours and an optional three-letter daylight time zone name. The daylight saving time rules to be used for a particular time zone are encoded in the time zone file; the format of the file allows U.S., Australian, and other rules to be encoded, and allows for situations where more than two time zone abbreviations are used. It was recognized that allowing the "TZ" environment variable to take on values such as "America/New_York" might cause "old" programs (that expect "TZ" to have a certain form) to operate incorrectly; consideration was given to using some other environment variable (for example, "TIMEZONE") to hold the string used to generate the time zone information file name. In the end, however, it was decided to continue using "TZ": it is widely used for time zone purposes; separately maintaining both "TZ" and "TIMEZONE" seemed a nuisance; and systems where "new" forms of "TZ" might cause problems can simply use TZ values such as "EST5EDT" which can be used both by "new" programs (a la POSIX) and "old" programs (as zone names and offsets). * The code supports platforms with a UT offset member in struct tm, e.g., tm_gmtoff. * The code supports platforms with a time zone abbreviation member in struct tm, e.g., tm_zone. * Since the "TZ" environment variable can now be used to control time conversion, the "daylight" and "timezone" variables are no longer needed. (These variables are defined and set by "tzset"; however, their values will not be used by "localtime.") * Functions tzalloc, tzfree, localtime_rz, and mktime_z for more-efficient thread-safe applications that need to use multiple time zones. The tzalloc and tzfree functions allocate and free objects of type timezone_t, and localtime_rz and mktime_z are like localtime_r and mktime with an extra timezone_t argument. The functions were inspired by NetBSD. * A function "tzsetwall" has been added to arrange for the system's best approximation to local wall clock time to be delivered by subsequent calls to "localtime." Source code for portable applications that "must" run on local wall clock time should call "tzsetwall();" if such code is moved to "old" systems that don't provide tzsetwall, you won't be able to generate an executable program. (These time zone functions also arrange for local wall clock time to be used if tzset is called - directly or indirectly - and there's no "TZ" environment variable; portable applications should not, however, rely on this behavior since it's not the way SVR2 systems behave.) * Negative time_t values are supported, on systems where time_t is signed. * These functions can account for leap seconds, thanks to Bradley White. Points of interest to folks with other systems: * Code compatible with this package is already part of many platforms, including GNU/Linux, Android, the BSDs, Chromium OS, Cygwin, AIX, iOS, BlackBery 10, macOS, Microsoft Windows, OpenVMS, and Solaris. On such hosts, the primary use of this package is to update obsolete time zone rule tables. To do this, you may need to compile the time zone compiler 'zic' supplied with this package instead of using the system 'zic', since the format of zic's input is occasionally extended, and a platform may still be shipping an older zic. * The UNIX Version 7 "timezone" function is not present in this package; it's impossible to reliably map timezone's arguments (a "minutes west of GMT" value and a "daylight saving time in effect" flag) to a time zone abbreviation, and we refuse to guess. Programs that in the past used the timezone function may now examine tzname[localtime(&clock)->tm_isdst] to learn the correct time zone abbreviation to use. Alternatively, use localtime(&clock)->tm_zone if this has been enabled. * The 4.2BSD gettimeofday function is not used in this package. This formerly let users obtain the current UTC offset and DST flag, but this functionality was removed in later versions of BSD. * In SVR2, time conversion fails for near-minimum or near-maximum time_t values when doing conversions for places that don't use UT. This package takes care to do these conversions correctly. A comment in the source code tells how to get compatibly wrong results. The functions that are conditionally compiled if STD_INSPIRED is defined should, at this point, be looked on primarily as food for thought. They are not in any sense "standard compatible" - some are not, in fact, specified in *any* standard. They do, however, represent responses of various authors to standardization proposals. Other time conversion proposals, in particular the one developed by folks at Hewlett Packard, offer a wider selection of functions that provide capabilities beyond those provided here. The absence of such functions from this package is not meant to discourage the development, standardization, or use of such functions. Rather, their absence reflects the decision to make this package contain valid extensions to POSIX, to ensure its broad acceptability. If more powerful time conversion functions can be standardized, so much the better. ----- Interface stability ----- The tz code and data supply the following interfaces: * A set of zone names as per "Names of time zone rules" above. * Library functions described in "Time and date functions" above. * The programs tzselect, zdump, and zic, documented in their man pages. * The format of zic input files, documented in the zic man page. * The format of zic output files, documented in the tzfile man page. * The format of zone table files, documented in zone1970.tab. * The format of the country code file, documented in iso3166.tab. * The version number of the code and data, as the first line of the text file 'version' in each release. Interface changes in a release attempt to preserve compatibility with recent releases. For example, tz data files typically do not rely on recently-added zic features, so that users can run older zic versions to process newer data files. The tz-link.htm file describes how releases are tagged and distributed. Interfaces not listed above are less stable. For example, users should not rely on particular UT offsets or abbreviations for time stamps, as data entries are often based on guesswork and these guesses may be corrected or improved. ----- Calendrical issues ----- Calendrical issues are a bit out of scope for a time zone database, but they indicate the sort of problems that we would run into if we extended the time zone database further into the past. An excellent resource in this area is Nachum Dershowitz and Edward M. Reingold, Calendrical Calculations: Third Edition, Cambridge University Press (2008) . Other information and sources are given below. They sometimes disagree. France Gregorian calendar adopted 1582-12-20. French Revolutionary calendar used 1793-11-24 through 1805-12-31, and (in Paris only) 1871-05-06 through 1871-05-23. Russia From Chris Carrier (1996-12-02): On 1929-10-01 the Soviet Union instituted an "Eternal Calendar" with 30-day months plus 5 holidays, with a 5-day week. On 1931-12-01 it changed to a 6-day week; in 1934 it reverted to the Gregorian calendar while retaining the 6-day week; on 1940-06-27 it reverted to the 7-day week. With the 6-day week the usual days off were the 6th, 12th, 18th, 24th and 30th of the month. (Source: Evitiar Zerubavel, _The Seven Day Circle_) Mark Brader reported a similar story in "The Book of Calendars", edited by Frank Parise (1982, Facts on File, ISBN 0-8719-6467-8), page 377. But: From: Petteri Sulonen (via Usenet) Date: 14 Jan 1999 00:00:00 GMT ... If your source is correct, how come documents between 1929 and 1940 were still dated using the conventional, Gregorian calendar? I can post a scan of a document dated December 1, 1934, signed by Yenukidze, the secretary, on behalf of Kalinin, the President of the Executive Committee of the Supreme Soviet, if you like. Sweden (and Finland) From: Mark Brader Subject: Re: Gregorian reform - a part of locale? Date: 1996-07-06 In 1700, Denmark made the transition from Julian to Gregorian. Sweden decided to *start* a transition in 1700 as well, but rather than have one of those unsightly calendar gaps :-), they simply decreed that the next leap year after 1696 would be in 1744 - putting the whole country on a calendar different from both Julian and Gregorian for a period of 40 years. However, in 1704 something went wrong and the plan was not carried through; they did, after all, have a leap year that year. And one in 1708. In 1712 they gave it up and went back to Julian, putting 30 days in February that year!... Then in 1753, Sweden made the transition to Gregorian in the usual manner, getting there only 13 years behind the original schedule. (A previous posting of this story was challenged, and Swedish readers produced the following references to support it: "Tideräkning och historia" by Natanael Beckman (1924) and "Tid, en bok om tideräkning och kalenderväsen" by Lars-Olof Lodén (1968). Grotefend's data From: "Michael Palmer" [with one obvious typo fixed] Subject: Re: Gregorian Calendar (was Re: Another FHC related question Newsgroups: soc.genealogy.german Date: Tue, 9 Feb 1999 02:32:48 -800 ... The following is a(n incomplete) listing, arranged chronologically, of European states, with the date they converted from the Julian to the Gregorian calendar: 04/15 Oct 1582 - Italy (with exceptions), Spain, Portugal, Poland (Roman Catholics and Danzig only) 09/20 Dec 1582 - France, Lorraine 21 Dec 1582/ 01 Jan 1583 - Holland, Brabant, Flanders, Hennegau 10/21 Feb 1583 - bishopric of Liege (Lüttich) 13/24 Feb 1583 - bishopric of Augsburg 04/15 Oct 1583 - electorate of Trier 05/16 Oct 1583 - Bavaria, bishoprics of Freising, Eichstedt, Regensburg, Salzburg, Brixen 13/24 Oct 1583 - Austrian Oberelsaß and Breisgau 20/31 Oct 1583 - bishopric of Basel 02/13 Nov 1583 - duchy of Jülich-Berg 02/13 Nov 1583 - electorate and city of Köln 04/15 Nov 1583 - bishopric of Würzburg 11/22 Nov 1583 - electorate of Mainz 16/27 Nov 1583 - bishopric of Strassburg and the margraviate of Baden 17/28 Nov 1583 - bishopric of Münster and duchy of Cleve 14/25 Dec 1583 - Steiermark 06/17 Jan 1584 - Austria and Bohemia 11/22 Jan 1584 - Lucerne, Uri, Schwyz, Zug, Freiburg, Solothurn 12/23 Jan 1584 - Silesia and the Lausitz 22 Jan/ 02 Feb 1584 - Hungary (legally on 21 Oct 1587) Jun 1584 - Unterwalden 01/12 Jul 1584 - duchy of Westfalen 16/27 Jun 1585 - bishopric of Paderborn 14/25 Dec 1590 - Transylvania 22 Aug/ 02 Sep 1612 - duchy of Prussia 13/24 Dec 1614 - Pfalz-Neuburg 1617 - duchy of Kurland (reverted to the Julian calendar in 1796) 1624 - bishopric of Osnabrück 1630 - bishopric of Minden 15/26 Mar 1631 - bishopric of Hildesheim 1655 - Kanton Wallis 05/16 Feb 1682 - city of Strassburg 18 Feb/ 01 Mar 1700 - Protestant Germany (including Swedish possessions in Germany), Denmark, Norway 30 Jun/ 12 Jul 1700 - Gelderland, Zutphen 10 Nov/ 12 Dec 1700 - Utrecht, Overijssel 31 Dec 1700/ 12 Jan 1701 - Friesland, Groningen, Zürich, Bern, Basel, Geneva, Turgau, and Schaffhausen 1724 - Glarus, Appenzell, and the city of St. Gallen 01 Jan 1750 - Pisa and Florence 02/14 Sep 1752 - Great Britain 17 Feb/ 01 Mar 1753 - Sweden 1760-1812 - Graubünden The Russian empire (including Finland and the Baltic states) did not convert to the Gregorian calendar until the Soviet revolution of 1917. Source: H. Grotefend, _Taschenbuch der Zeitrechnung des deutschen Mittelalters und der Neuzeit_, herausgegeben von Dr. O. Grotefend (Hannover: Hahnsche Buchhandlung, 1941), pp. 26-28. ----- Time and time zones on Mars ----- Some people's work schedules use Mars time. Jet Propulsion Laboratory (JPL) coordinators have kept Mars time on and off at least since 1997 for the Mars Pathfinder mission. Some of their family members have also adapted to Mars time. Dozens of special Mars watches were built for JPL workers who kept Mars time during the Mars Exploration Rovers mission (2004). These timepieces look like normal Seikos and Citizens but use Mars seconds rather than terrestrial seconds. A Mars solar day is called a "sol" and has a mean period equal to about 24 hours 39 minutes 35.244 seconds in terrestrial time. It is divided into a conventional 24-hour clock, so each Mars second equals about 1.02749125 terrestrial seconds. The prime meridian of Mars goes through the center of the crater Airy-0, named in honor of the British astronomer who built the Greenwich telescope that defines Earth's prime meridian. Mean solar time on the Mars prime meridian is called Mars Coordinated Time (MTC). Each landed mission on Mars has adopted a different reference for solar time keeping, so there is no real standard for Mars time zones. For example, the Mars Exploration Rover project (2004) defined two time zones "Local Solar Time A" and "Local Solar Time B" for its two missions, each zone designed so that its time equals local true solar time at approximately the middle of the nominal mission. Such a "time zone" is not particularly suited for any application other than the mission itself. Many calendars have been proposed for Mars, but none have achieved wide acceptance. Astronomers often use Mars Sol Date (MSD) which is a sequential count of Mars solar days elapsed since about 1873-12-29 12:00 GMT. The tz database does not currently support Mars time, but it is documented here in the hopes that support will be added eventually. Sources: Michael Allison and Robert Schmunk, "Technical Notes on Mars Solar Time as Adopted by the Mars24 Sunclock" (2012-08-08). Jia-Rui Chong, "Workdays Fit for a Martian", Los Angeles Times (2004-01-14), pp A1, A20-A21. Tom Chmielewski, "Jet Lag Is Worse on Mars", The Atlantic (2015-02-26) ----- This file is in the public domain, so clarified as of 2009-05-17 by Arthur David Olson. ----- Local Variables: coding: utf-8 End: @ 1.22 log @welcome to 2016h @ text @d11 1 d43 1 a43 1 IEEE Std 1003.1, 2013 Edition d212 13 d242 1 a242 1 as before; e.g. 'VLAST' for VLAdivostok Summer Time. d359 1 a359 1 this unreliability. d361 21 a381 9 * As for leap seconds, civil time was not based on atomic time before 1972, and we don't know the history of earth's rotation accurately enough to map SI seconds to historical solar time to more than about one-hour accuracy. See: Morrison LV, Stephenson FR. Historical values of the Earth's clock error Delta T and the calculation of eclipses. J Hist Astron. 2004;35:327-36 ; Historical values of the Earth's clock error. J Hist Astron. 2005;36:339 . d630 8 a637 4 When these interfaces are changed, an effort is made to preserve backward compatibility. For example, tz data files typically do not rely on recently-added zic features, so that users can run older zic versions to process newer data files. @ 1.22.2.1 log @Sync with HEAD @ text @a10 1 Interface stability d42 1 a42 1 IEEE Std 1003.1-2008, 2016 Edition a210 13 Use current abbreviations for older timestamps to avoid confusion. For example, in 1910 a common English abbreviation for UT +01 in central Europe was 'MEZ' (short for both "Middle European Zone" and for "Mitteleuropäische Zeit" in German). Nowadays 'CET' ("Central European Time") is more common in English, and the database uses 'CET' even for circa-1910 timestamps as this is less confusing for modern users and avoids the need for determining when 'CET' supplanted 'MEZ' in common usage. Use a consistent style in a zone's history. For example, if a zone's history tends to use numeric abbreviations and a particular entry could go either way, use a numeric abbreviation. d228 1 a228 1 as before; e.g. 'CHAST' for CHAtham Summer Time. d345 1 a345 1 clock error. d347 9 a355 21 * The tz database assumes Universal Time (UT) as an origin, even though UT is not standardized for older time stamps. In the tz database commentary, UT denotes a family of time standards that includes Coordinated Universal Time (UTC) along with other variants such as UT1 and GMT, with days starting at midnight. Although UT equals UTC for modern time stamps, UTC was not defined until 1960, so commentary uses the more-general abbreviation UT for time stamps that might predate 1960. Since UT, UT1, etc. disagree slightly, and since pre-1972 UTC seconds varied in length, interpretation of older time stamps can be problematic when subsecond accuracy is needed. * Civil time was not based on atomic time before 1972, and we don't know the history of earth's rotation accurately enough to map SI seconds to historical solar time to more than about one-hour accuracy. See: Stephenson FR, Morrison LV, Hohenkerk CY. Measurement of the Earth's rotation: 720 BC to AD 2015. Proc Royal Soc A. 2016 Dec 7;472:20160404. http://dx.doi.org/10.1098/rspa.2016.0404 Also see: Espenak F. Uncertainty in Delta T (ΔT). http://eclipse.gsfc.nasa.gov/SEhelp/uncertainty2004.html d604 4 a607 8 * The version number of the code and data, as the first line of the text file 'version' in each release. Interface changes in a release attempt to preserve compatibility with recent releases. For example, tz data files typically do not rely on recently-added zic features, so that users can run older zic versions to process newer data files. The tz-link.htm file describes how releases are tagged and distributed. @ 1.21 log @merge tzcode2016g @ text @d448 4 d461 5 d506 5 a510 5 * To handle places where more than two time zone abbreviations are used, the functions "localtime" and "gmtime" set tzname[tmp->tm_isdst] (where "tmp" is the value the function returns) to the time zone abbreviation to be used. This differs from POSIX, where the elements of tzname are only changed as a result of calls to tzset. d517 6 a522 3 * The "localtime" function has been set up to deliver correct results for near-minimum or near-maximum time_t values. (A comment in the source code tells how to get compatibly wrong results). d541 3 a543 2 * This package is already part of many POSIX-compliant hosts, including BSD, HP, Linux, Network Appliance, SCO, SGI, and Sun. d548 2 a549 2 since the format of zic's input changed slightly in late 1994, and many vendors still do not support the new input format. d567 2 d586 29 @ 1.20 log @welcome to tzcond-2016f @ text @d326 1 a326 1 1937 Netherlands clocks were legally UT+00:19:32.13, but the tz @ 1.19 log @Sync with 2016b @ text @d230 4 a233 3 Use UT (with time zone abbreviation 'zzz') for locations while uninhabited. The 'zzz' mnemonic is that these locations are, in some sense, asleep. @ 1.19.2.1 log @Sync with HEAD @ text @d230 3 a232 4 Use UT (with time zone abbreviation '-00') for locations while uninhabited. The leading '-' is a flag that the time zone is in some sense undefined; this notation is derived from Internet RFC 3339. d325 1 a325 1 1937 Netherlands clocks were legally UT +00:19:32.13, but the tz a446 4 * The TZ environment variable is process-global, which makes it hard to write efficient, thread-safe applications that need access to multiple time zones. a455 5 * POSIX provides no convenient and efficient way to determine the UT offset and time zone abbreviation of arbitrary time stamps, particularly for time zone settings that do not fit into the POSIX model. d496 5 a500 5 * The code supports platforms with a UT offset member in struct tm, e.g., tm_gmtoff. * The code supports platforms with a time zone abbreviation member in struct tm, e.g., tm_zone. d507 3 a509 6 * Functions tzalloc, tzfree, localtime_rz, and mktime_z for more-efficient thread-safe applications that need to use multiple time zones. The tzalloc and tzfree functions allocate and free objects of type timezone_t, and localtime_rz and mktime_z are like localtime_r and mktime with an extra timezone_t argument. The functions were inspired by NetBSD. d528 2 a529 3 * Code compatible with this package is already part of many platforms, including GNU/Linux, Android, the BSDs, Chromium OS, Cygwin, AIX, iOS, BlackBery 10, macOS, Microsoft Windows, OpenVMS, and Solaris. d534 2 a535 2 since the format of zic's input is occasionally extended, and a platform may still be shipping an older zic. a552 2 A comment in the source code tells how to get compatibly wrong results. a569 29 ----- Interface stability ----- The tz code and data supply the following interfaces: * A set of zone names as per "Names of time zone rules" above. * Library functions described in "Time and date functions" above. * The programs tzselect, zdump, and zic, documented in their man pages. * The format of zic input files, documented in the zic man page. * The format of zic output files, documented in the tzfile man page. * The format of zone table files, documented in zone1970.tab. * The format of the country code file, documented in iso3166.tab. When these interfaces are changed, an effort is made to preserve backward compatibility. For example, tz data files typically do not rely on recently-added zic features, so that users can run older zic versions to process newer data files. Interfaces not listed above are less stable. For example, users should not rely on particular UT offsets or abbreviations for time stamps, as data entries are often based on guesswork and these guesses may be corrected or improved. @ 1.19.2.2 log @Sync with HEAD @ text @a10 1 Interface stability d42 1 a42 1 IEEE Std 1003.1-2008, 2016 Edition a210 13 Use current abbreviations for older timestamps to avoid confusion. For example, in 1910 a common English abbreviation for UT +01 in central Europe was 'MEZ' (short for both "Middle European Zone" and for "Mitteleuropäische Zeit" in German). Nowadays 'CET' ("Central European Time") is more common in English, and the database uses 'CET' even for circa-1910 timestamps as this is less confusing for modern users and avoids the need for determining when 'CET' supplanted 'MEZ' in common usage. Use a consistent style in a zone's history. For example, if a zone's history tends to use numeric abbreviations and a particular entry could go either way, use a numeric abbreviation. d228 1 a228 1 as before; e.g. 'CHAST' for CHAtham Summer Time. d345 1 a345 1 clock error. d347 9 a355 21 * The tz database assumes Universal Time (UT) as an origin, even though UT is not standardized for older time stamps. In the tz database commentary, UT denotes a family of time standards that includes Coordinated Universal Time (UTC) along with other variants such as UT1 and GMT, with days starting at midnight. Although UT equals UTC for modern time stamps, UTC was not defined until 1960, so commentary uses the more-general abbreviation UT for time stamps that might predate 1960. Since UT, UT1, etc. disagree slightly, and since pre-1972 UTC seconds varied in length, interpretation of older time stamps can be problematic when subsecond accuracy is needed. * Civil time was not based on atomic time before 1972, and we don't know the history of earth's rotation accurately enough to map SI seconds to historical solar time to more than about one-hour accuracy. See: Stephenson FR, Morrison LV, Hohenkerk CY. Measurement of the Earth's rotation: 720 BC to AD 2015. Proc Royal Soc A. 2016 Dec 7;472:20160404. http://dx.doi.org/10.1098/rspa.2016.0404 Also see: Espenak F. Uncertainty in Delta T (ΔT). http://eclipse.gsfc.nasa.gov/SEhelp/uncertainty2004.html d604 4 a607 8 * The version number of the code and data, as the first line of the text file 'version' in each release. Interface changes in a release attempt to preserve compatibility with recent releases. For example, tz data files typically do not rely on recently-added zic features, so that users can run older zic versions to process newer data files. The tz-link.htm file describes how releases are tagged and distributed. @ 1.18 log @merge 2015f @ text @d176 1 a176 1 Use abbreviations that consist of three or more ASCII letters. d184 5 a188 1 preferred "ChST", so the rule has been relaxed. d190 4 a193 11 This rule guarantees that all abbreviations could have been specified by a POSIX TZ string. POSIX requires at least three characters for an abbreviation. POSIX through 2000 says that an abbreviation cannot start with ':', and cannot contain ',', '-', '+', NUL, or a digit. POSIX from 2001 on changes this rule to say that an abbreviation can contain only '-', '+', and alphanumeric characters from the portable character set in the current locale. To be portable to both sets of rules, an abbreviation must therefore use only ASCII letters. d263 9 a271 1 of entries, perhaps hundreds. @ 1.17 log @merge 2015b @ text @d1 2 a2 2 This file is in the public domain, so clarified as of 2009-05-17 by Arthur David Olson. a5 1 Time and date functions d7 1 a7 1 Names of time zone rule files d9 2 a13 1 ----- Time and date functions ----- d15 25 a39 3 These time and date functions are upwards compatible with those of POSIX, an international standard for UNIX-like systems. As of this writing, the current edition of POSIX is: a44 1 POSIX has the following properties and limitations. a45 6 * In POSIX, time display in a process is controlled by the environment variable TZ. Unfortunately, the POSIX TZ string takes a form that is hard to describe and is error-prone in practice. Also, POSIX TZ strings can't deal with other (for example, Israeli) daylight saving time rules, or situations where more than two time zone abbreviations are used in an area. d47 1 a47 1 The POSIX TZ string takes the following form: d49 7 a55 1 stdoffset[dst[offset][,date[/time],date[/time]]] d57 2 a58 1 where: d60 11 a70 31 std and dst are 3 or more characters specifying the standard and daylight saving time (DST) zone names. Starting with POSIX.1-2001, std and dst may also be in a quoted form like ""; this allows "+" and "-" in the names. offset is of the form '[+-]hh:[mm[:ss]]' and specifies the offset west of UT. 'hh' may be a single digit; 0<=hh<=24. The default DST offset is one hour ahead of standard time. date[/time],date[/time] specifies the beginning and end of DST. If this is absent, the system supplies its own rules for DST, and these can differ from year to year; typically US DST rules are used. time takes the form 'hh:[mm[:ss]]' and defaults to 02:00. This is the same format as the offset, except that a leading '+' or '-' is not allowed. date takes one of the following forms: Jn (1<=n<=365) origin-1 day number not counting February 29 n (0<=n<=365) origin-0 day number counting February 29 if present Mm.n.d (0[Sunday]<=d<=6[Saturday], 1<=n<=5, 1<=m<=12) for the dth day of week n of month m of the year, where week 1 is the first week in which day d appears, and '5' stands for the last week in which day d appears (which may be either the 4th or 5th week). Typically, this is the only useful form; the n and Jn forms are rarely used. d72 1 a72 2 Here is an example POSIX TZ string, for US Pacific time using rules appropriate from 1987 through 2006: d74 1 a74 1 TZ='PST8PDT,M4.1.0/02:00,M10.5.0/02:00' d76 5 a80 3 This POSIX TZ string is hard to remember, and mishandles time stamps before 1987 and after 2006. With this package you can use this instead: d82 2 a83 1 TZ='America/Los_Angeles' d85 56 a140 6 * POSIX does not define the exact meaning of TZ values like "EST5EDT". Typically the current US DST rules are used to interpret such values, but this means that the US DST rules are compiled into each program that does time conversion. This means that when US time conversion rules change (as in the United States in 1987), all programs that do time conversion must be recompiled to ensure proper results. d142 6 a147 8 * In POSIX, there's no tamper-proof way for a process to learn the system's best idea of local wall clock. (This is important for applications that an administrator wants used only at certain times - without regard to whether the user has fiddled the "TZ" environment variable. While an administrator can "do everything in UTC" to get around the problem, doing so is inconvenient and precludes handling daylight saving time shifts - as might be required to limit phone calls to off-peak hours.) d149 6 a154 1 * POSIX requires that systems ignore leap seconds. d156 7 a162 12 * The tz code attempts to support all the time_t implementations allowed by POSIX. The time_t type represents a nonnegative count of seconds since 1970-01-01 00:00:00 UTC, ignoring leap seconds. In practice, time_t is usually a signed 64- or 32-bit integer; 32-bit signed time_t values stop working after 2038-01-19 03:14:07 UTC, so new implementations these days typically use a signed 64-bit integer. Unsigned 32-bit integers are used on one or two platforms, and 36-bit and 40-bit integers are also used occasionally. Although earlier POSIX versions allowed time_t to be a floating-point type, this was not supported by any practical systems, and POSIX.1-2013 and the tz code both require time_t to be an integer type. d164 3 a166 1 These are the extensions that have been made to the POSIX functions: a167 9 * The "TZ" environment variable is used in generating the name of a file from which time zone information is read (or is interpreted a la POSIX); "TZ" is no longer constrained to be a three-letter time zone name followed by a number of hours and an optional three-letter daylight time zone name. The daylight saving time rules to be used for a particular time zone are encoded in the time zone file; the format of the file allows U.S., Australian, and other rules to be encoded, and allows for situations where more than two time zone abbreviations are used. d169 1 a169 12 It was recognized that allowing the "TZ" environment variable to take on values such as "America/New_York" might cause "old" programs (that expect "TZ" to have a certain form) to operate incorrectly; consideration was given to using some other environment variable (for example, "TIMEZONE") to hold the string used to generate the time zone information file name. In the end, however, it was decided to continue using "TZ": it is widely used for time zone purposes; separately maintaining both "TZ" and "TIMEZONE" seemed a nuisance; and systems where "new" forms of "TZ" might cause problems can simply use TZ values such as "EST5EDT" which can be used both by "new" programs (a la POSIX) and "old" programs (as zone names and offsets). d171 4 a174 5 * To handle places where more than two time zone abbreviations are used, the functions "localtime" and "gmtime" set tzname[tmp->tm_isdst] (where "tmp" is the value the function returns) to the time zone abbreviation to be used. This differs from POSIX, where the elements of tzname are only changed as a result of calls to tzset. d176 9 a184 4 * Since the "TZ" environment variable can now be used to control time conversion, the "daylight" and "timezone" variables are no longer needed. (These variables are defined and set by "tzset"; however, their values will not be used by "localtime.") d186 11 a196 3 * The "localtime" function has been set up to deliver correct results for near-minimum or near-maximum time_t values. (A comment in the source code tells how to get compatibly wrong results). d198 5 a202 10 * A function "tzsetwall" has been added to arrange for the system's best approximation to local wall clock time to be delivered by subsequent calls to "localtime." Source code for portable applications that "must" run on local wall clock time should call "tzsetwall();" if such code is moved to "old" systems that don't provide tzsetwall, you won't be able to generate an executable program. (These time zone functions also arrange for local wall clock time to be used if tzset is called - directly or indirectly - and there's no "TZ" environment variable; portable applications should not, however, rely on this behavior since it's not the way SVR2 systems behave.) d204 3 a206 1 * Negative time_t values are supported, on systems where time_t is signed. d208 2 a209 1 * These functions can account for leap seconds, thanks to Bradley White. d211 2 a212 1 Points of interest to folks with other systems: d214 5 a218 8 * This package is already part of many POSIX-compliant hosts, including BSD, HP, Linux, Network Appliance, SCO, SGI, and Sun. On such hosts, the primary use of this package is to update obsolete time zone rule tables. To do this, you may need to compile the time zone compiler 'zic' supplied with this package instead of using the system 'zic', since the format of zic's input changed slightly in late 1994, and many vendors still do not support the new input format. d220 4 a223 8 * The UNIX Version 7 "timezone" function is not present in this package; it's impossible to reliably map timezone's arguments (a "minutes west of GMT" value and a "daylight saving time in effect" flag) to a time zone abbreviation, and we refuse to guess. Programs that in the past used the timezone function may now examine tzname[localtime(&clock)->tm_isdst] to learn the correct time zone abbreviation to use. Alternatively, use localtime(&clock)->tm_zone if this has been enabled. d225 7 a231 3 * The 4.2BSD gettimeofday function is not used in this package. This formerly let users obtain the current UTC offset and DST flag, but this functionality was removed in later versions of BSD. d233 3 a235 3 * In SVR2, time conversion fails for near-minimum or near-maximum time_t values when doing conversions for places that don't use UT. This package takes care to do these conversions correctly. d237 5 a241 36 The functions that are conditionally compiled if STD_INSPIRED is defined should, at this point, be looked on primarily as food for thought. They are not in any sense "standard compatible" - some are not, in fact, specified in *any* standard. They do, however, represent responses of various authors to standardization proposals. Other time conversion proposals, in particular the one developed by folks at Hewlett Packard, offer a wider selection of functions that provide capabilities beyond those provided here. The absence of such functions from this package is not meant to discourage the development, standardization, or use of such functions. Rather, their absence reflects the decision to make this package contain valid extensions to POSIX, to ensure its broad acceptability. If more powerful time conversion functions can be standardized, so much the better. ----- Scope of the tz database ----- The tz database attempts to record the history and predicted future of all computer-based clocks that track civil time. To represent this data, the world is partitioned into regions whose clocks all agree about time stamps that occur after the somewhat-arbitrary cutoff point of the POSIX Epoch (1970-01-01 00:00:00 UTC). For each such region, the database records all known clock transitions, and labels the region with a notable location. Although 1970 is a somewhat-arbitrary cutoff, there are significant challenges to moving the cutoff earlier even by a decade or two, due to the wide variety of local practices before computer timekeeping became prevalent. Clock transitions before 1970 are recorded for each such location, because most POSIX-compatible systems support negative time stamps and could misbehave if data entries were omitted for pre-1970 transitions. However, the database is not designed for and does not suffice for applications requiring accurate handling of all past times everywhere, as it would take far too much effort and guesswork to record all details of pre-1970 civil timekeeping. d372 54 a425 1 ----- Names of time zone rule files ----- d427 1 a427 2 The time zone rule file naming conventions attempt to strike a balance among the following goals: d429 3 a431 12 * Uniquely identify every national region where clocks have all agreed since 1970. This is essential for the intended use: static clocks keeping local civil time. * Indicate to humans as to where that region is. This simplifies use. * Be robust in the presence of political changes. This reduces the number of updates and backward-compatibility hacks. For example, names of countries are ordinarily not used, to avoid incompatibilities when countries change their name (e.g. Zaire->Congo) or when locations change countries (e.g. Hong Kong from UK colony to China). d433 1 a433 2 * Be portable to a wide variety of implementations. This promotes use of the technology. d435 6 a440 2 * Use a consistent naming convention over the entire world. This simplifies both use and maintenance. d442 8 a449 6 This naming convention is not intended for use by inexperienced users to select TZ values by themselves (though they can of course examine and reuse existing settings). Distributors should provide documentation and/or a simple selection interface that explains the names; see the 'tzselect' program supplied with this distribution for one example. d451 1 a451 5 Names normally have the form AREA/LOCATION, where AREA is the name of a continent or ocean, and LOCATION is the name of a specific location within that region. North and South America share the same area, 'America'. Typical names are 'Africa/Cairo', 'America/New_York', and 'Pacific/Honolulu'. d453 12 a464 2 Here are the general rules used for choosing location names, in decreasing order of importance: d466 1 a466 56 Use only valid POSIX file name components (i.e., the parts of names other than '/'). Do not use the file name components '.' and '..'. Within a file name component, use only ASCII letters, '.', '-' and '_'. Do not use digits, as that might create an ambiguity with POSIX TZ strings. A file name component must not exceed 14 characters or start with '-'. E.g., prefer 'Brunei' to 'Bandar_Seri_Begawan'. Exceptions: see the discussion of legacy names below. A name must not be empty, or contain '//', or start or end with '/'. Do not use names that differ only in case. Although the reference implementation is case-sensitive, some other implementations are not, and they would mishandle names differing only in case. If one name A is an initial prefix of another name AB (ignoring case), then B must not start with '/', as a regular file cannot have the same name as a directory in POSIX. For example, 'America/New_York' precludes 'America/New_York/Bronx'. Uninhabited regions like the North Pole and Bouvet Island do not need locations, since local time is not defined there. There should typically be at least one name for each ISO 3166-1 officially assigned two-letter code for an inhabited country or territory. If all the clocks in a region have agreed since 1970, don't bother to include more than one location even if subregions' clocks disagreed before 1970. Otherwise these tables would become annoyingly large. If a name is ambiguous, use a less ambiguous alternative; e.g. many cities are named San José and Georgetown, so prefer 'Costa_Rica' to 'San_Jose' and 'Guyana' to 'Georgetown'. Keep locations compact. Use cities or small islands, not countries or regions, so that any future time zone changes do not split locations into different time zones. E.g. prefer 'Paris' to 'France', since France has had multiple time zones. Use mainstream English spelling, e.g. prefer 'Rome' to 'Roma', and prefer 'Athens' to the Greek 'Αθήνα' or the Romanized 'Athína'. The POSIX file name restrictions encourage this rule. Use the most populous among locations in a zone, e.g. prefer 'Shanghai' to 'Beijing'. Among locations with similar populations, pick the best-known location, e.g. prefer 'Rome' to 'Milan'. Use the singular form, e.g. prefer 'Canary' to 'Canaries'. Omit common suffixes like '_Islands' and '_City', unless that would lead to ambiguity. E.g. prefer 'Cayman' to 'Cayman_Islands' and 'Guatemala' to 'Guatemala_City', but prefer 'Mexico_City' to 'Mexico' because the country of Mexico has several time zones. Use '_' to represent a space. Omit '.' from abbreviations in names, e.g. prefer 'St_Helena' to 'St._Helena'. Do not change established names if they only marginally violate the above rules. For example, don't change the existing name 'Rome' to 'Milan' merely because Milan's population has grown to be somewhat greater than Rome's. If a name is changed, put its old spelling in the 'backward' file. This means old spellings will continue to work. d468 9 a476 6 The file 'zone1970.tab' lists geographical locations used to name time zone rule files. It is intended to be an exhaustive list of names for geographic regions as described above; this is a subset of the names in the data. Although a 'zone1970.tab' location's longitude corresponds to its LMT offset with one hour for every 15 degrees east longitude, this relationship is not exact. d478 12 a489 6 Older versions of this package used a different naming scheme, and these older names are still supported. See the file 'backward' for most of these older names (e.g., 'US/Eastern' instead of 'America/New_York'). The other old-fashioned names still supported are 'WET', 'CET', 'MET', and 'EET' (see the file 'europe'). d491 5 a495 7 Older versions of this package defined legacy names that are incompatible with the first rule of location names, but which are still supported. These legacy names are mostly defined in the file 'etcetera'. Also, the file 'backward' defines the legacy names 'GMT0', 'GMT-0', 'GMT+0' and 'Canada/East-Saskatchewan', and the file 'northamerica' defines the legacy names 'EST5EDT', 'CST6CDT', 'MST7MDT', and 'PST8PDT'. d497 4 a500 3 Excluding 'backward' should not affect the other data. If 'backward' is excluded, excluding 'etcetera' should not affect the remaining data. d502 3 d506 10 a515 1 ----- Time zone abbreviations ----- d517 1 a517 4 When this package is installed, it generates time zone abbreviations like 'EST' to be compatible with human tradition and POSIX. Here are the general rules used for choosing time zone abbreviations, in decreasing order of importance: d519 1 a519 9 Use abbreviations that consist of three or more ASCII letters. Previous editions of this database also used characters like ' ' and '?', but these characters have a special meaning to the shell and cause commands like set `date` to have unexpected effects. Previous editions of this rule required upper-case letters, but the Congressman who introduced Chamorro Standard Time preferred "ChST", so the rule has been relaxed. d521 1 a521 11 This rule guarantees that all abbreviations could have been specified by a POSIX TZ string. POSIX requires at least three characters for an abbreviation. POSIX through 2000 says that an abbreviation cannot start with ':', and cannot contain ',', '-', '+', NUL, or a digit. POSIX from 2001 on changes this rule to say that an abbreviation can contain only '-', '+', and alphanumeric characters from the portable character set in the current locale. To be portable to both sets of rules, an abbreviation must therefore use only ASCII letters. d523 8 a530 5 Use abbreviations that are in common use among English-speakers, e.g. 'EST' for Eastern Standard Time in North America. We assume that applications translate them to other languages as part of the normal localization process; for example, a French application might translate 'EST' to 'HNE'. d532 8 a539 3 For zones whose times are taken from a city's longitude, use the traditional xMT notation, e.g. 'PMT' for Paris Mean Time. The only name like this in current use is 'GMT'. d541 3 a543 4 If there is no common English abbreviation, abbreviate the English translation of the usual phrase used by native speakers. If this is not available or is a phrase mentioning the country (e.g. "Cape Verde Time"), then: d545 3 a547 7 When a country is identified with a single or principal zone, append 'T' to the country's ISO code, e.g. 'CVT' for Cape Verde Time. For summer time append 'ST'; for double summer time append 'DST'; etc. Otherwise, take the first three letters of an English place name identifying each zone and append 'T', 'ST', etc. as before; e.g. 'VLAST' for VLAdivostok Summer Time. d549 5 a553 2 Use 'LMT' for local mean time of locations before the introduction of standard time; see "Scope of the tz database". d555 8 a562 9 Use UT (with time zone abbreviation 'zzz') for locations while uninhabited. The 'zzz' mnemonic is that these locations are, in some sense, asleep. Application writers should note that these abbreviations are ambiguous in practice: e.g. 'CST' has a different meaning in China than it does in the United States. In new applications, it's often better to use numeric UT offsets like '-0600' instead of time zone abbreviations like 'CST'; this avoids the ambiguity. d783 5 @ 1.16 log @Sync with tzcode2014h @ text @d720 5 a724 3 Some people have adjusted their work schedules to fit Mars time. Dozens of special Mars watches were built for Jet Propulsion Laboratory workers who kept Mars time during the Mars Exploration d765 2 @ 1.15 log @merge tzcode2014f via patch @ text @d106 1 a106 1 and 36-bit integers are also used occasionally. d130 1 a130 1 to continue using "TZ": it is widely used for time zone purposes; d226 1 a226 1 could misbehave if data were omitted for pre-1970 transitions. d236 3 a238 3 Corrections are welcome and encouraged. Users requiring authoritative data should consult national standards bodies and the references cited in the database's comments. d249 1 a249 1 * The pre-1970 data in this database cover only a tiny sliver of how d257 1 a257 1 * Most of the pre-1970 data comes from unreliable sources, often d262 1 a262 1 and on the rare occasions when their old data are checked they are d285 2 a286 2 * The tz database does not record the earliest time for which a zone's data is thereafter valid for every location in the region. d321 1 a321 1 * The tz database models pre-standard time using the Gregorian d327 2 a328 2 * Early clocks were less reliable, and the data do not represent this unreliability. d348 1 a348 1 Ideally it would contain information about when the data are d713 1 a713 1 Source: H. Grotefend, _Taschenbuch der Zeitrechnung des deutschen d715 1 a715 1 (Hannover: Hahnsche Buchhandlung, 1941), pp. 26-28. @ 1.14 log @Welcome to tzcode 2013e: Changes affecting API The 'zic' command now outputs a dummy transition when far-future data can't be summarized using a TZ string, and uses a 402-year window rather than a 400-year window. For the current data, this affects only the Asia/Tehran file. It does not affect any of the time stamps that this file represents, so zdump outputs the same information as before. (Thanks to Andrew Main (Zefram).) The 'date' command has a new '-r' option, which lets you specify the integer time to display, a la FreeBSD. The 'tzselect' command has two new options '-c' and '-n', which lets you select a zone based on latitude and longitude. The 'zic' command's '-v' option now warns about constructs that require the new version-3 binary file format. (Thanks to Arthur David Olson for the suggestion.) Support for floating-point time_t has been removed. It was always dicey, and POSIX no longer requires it. (Thanks to Eric Blake for suggesting to the POSIX committee to remove it, and thanks to Alan Barrett, Clive D.W. Feather, Andy Heninger, Arthur David Olson, and Alois Treindl, for reporting bugs and elucidating some of the corners of the old floating-point implementation.) The signatures of 'offtime', 'timeoff', and 'gtime' have been changed back to the old practice of using 'long' to represent UT offsets. This had been inadvertently and mistakenly changed to 'int_fast32_t'. (Thanks to Christos Zoulos.) The code avoids undefined behavior on integer overflow in some more places, including gmtime, localtime, mktime and zdump. Changes affecting the zdump utility zdump now outputs "UT" when referring to Universal Time, not "UTC". "UTC" does not make sense for time stamps that predate the introduction of UTC, whereas "UT", a more-generic term, does. (Thanks to Steve Allen for clarifying UT vs UTC.) Data changes affecting behavior of tzselect and similar programs Country code BQ is now called the more-common name "Caribbean Netherlands" rather than the more-official "Bonaire, St Eustatius & Saba". Remove from zone.tab the names America/Montreal, America/Shiprock, and Antarctica/South_Pole, as they are equivalent to existing same-country-code zones for post-1970 time stamps. The data for these names are unchanged, so the names continue to work as before. Changes affecting code internals zic -c now runs way faster on 64-bit hosts when given large numbers. zic now uses vfprintf to avoid allocating and freeing some memory. tzselect now computes the list of continents from the data, rather than have it hard-coded. Minor changes pacify GCC 4.7.3 and GCC 4.8.1. Changes affecting the build procedure The 'leapseconds' file is now generated automatically from a new file 'leap-seconds.list', which is a copy of . A new source file 'leapseconds.awk' implements this. The goal is simplification of the future maintenance of 'leapseconds'. When building the 'posix' or 'right' subdirectories, if the subdirectory would be a copy of the default subdirectory, it is now made a symbolic link if that is supported. This saves about 2 MB of file system space. The links America/Shiprock and Antarctica/South_Pole have been moved to the 'backward' file. This affects only nondefault builds that omit 'backward'. Changes affecting documentation and commentary Changes to the 'tzfile' man page It now mentions that the binary file format may be extended in future versions by appending data. It now refers to the 'zdump' and 'zic' man pages. Changes to the 'zic' man page It lists conditions that elicit a warning with '-v'. It says that the behavior is unspecified when duplicate names are given, or if the source of one link is the target of another. Its examples are updated to match the latest data. The definition of white space has been clarified slightly. (Thanks to Michael Deckers.) Changes to the 'Theory' file There is a new section about the accuracy of the tz database, describing the many ways that errors can creep in, and explaining why so many of the pre-1970 time stamps are wrong or misleading (thanks to Steve Allen, Lester Caine, and Garrett Wollman for discussions that contributed to this). The 'Theory' file describes LMT better (this follows a suggestion by Guy Harris). It refers to the 2013 edition of POSIX rather than the 2004 edition. It's mentioned that excluding 'backward' should not affect the other data, and it suggests at least one zone.tab name per inhabited country (thanks to Stephen Colebourne). Some longstanding restrictions on names are documented, e.g., 'America/New_York' precludes 'America/New_York/Bronx'. It gives more reasons for the 1970 cutoff. It now mentions which time_t variants are supported, such as signed integer time_t. (Thanks to Paul Goyette for reporting typos in an experimental version of this change.) (Thanks to Philip Newton for correcting typos in these changes.) Documentation and commentary is more careful to distinguish UT in general from UTC in particular. (Thanks to Steve Allen.) Add a better source for the Zurich 1894 transition. (Thanks to Pierre-Yves Berger.) Update shapefile citations in tz-link.htm. (Thanks to Guy Harris.) @ text @d90 1 a90 1 applications that an administrator wants used only at certain times-- d94 1 a94 1 daylight saving time shifts--as might be required to limit phone d99 1 a99 1 * The tz code attempts attempts to support all the time_t implementations d159 1 a159 1 used if tzset is called--directly or indirectly--and there's no "TZ" d197 1 a197 1 not in any sense "standard compatible"--some are not, in fact, specified in d408 2 a409 1 to 'Bandar_Seri_Begawan'. d428 1 a428 1 e.g. many cities are named San Jose and Georgetown, so d435 1 a435 1 prefer 'Athens' to the true name (which uses Greek letters). d458 1 a458 1 The file 'zone.tab' lists geographical locations used to name time d461 1 a461 1 names in the data. Although a 'zone.tab' location's longitude d468 1 a468 2 (e.g. 'US/Eastern' instead of 'America/New_York'); excluding 'backward' should not affect the other data. d472 12 d545 1 a545 1 in practice: e.g. 'EST' has a different meaning in Australia than d547 2 a548 2 to use numeric UT offsets like '-0500' instead of time zone abbreviations like 'EST'; this avoids the ambiguity. d557 3 a559 4 Calendrical Calculations: Third Edition , Cambridge University Press (2008). Other information and sources are given below. They sometimes disagree. d588 1 a588 1 If your source is correct, how come documents between 1929 -- 1940 were d600 2 a601 3 Subject: Re: Gregorian reform -- a part of locale? d607 1 a607 1 year after 1696 would be in 1744 -- putting the whole country on a calendar d619 3 a621 3 produced the following references to support it: "Tiderakning och historia" by Natanael Beckman (1924) and "Tid, en bok om tiderakning och kalendervasen" by Lars-Olof Lode'n (no date was given).) d642 1 a642 1 10/21 Feb 1583 - bishopric of Liege (L"uttich) d647 1 a647 1 13/24 Oct 1583 - Austrian Oberelsass and Breisgau d649 3 a651 3 02/13 Nov 1583 - duchy of J"ulich-Berg 02/13 Nov 1583 - electorate and city of K"oln 04/15 Nov 1583 - bishopric of W"urzburg d654 1 a654 1 17/28 Nov 1583 - bishopric of M"unster and duchy of Cleve d658 1 a658 1 11/22 Jan 1584 - Luzern, Uri, Schwyz, Zug, Freiburg, Solothurn d677 1 a677 1 1624 - bishopric of Osnabr"uck d696 1 a696 1 12 Jan 1701 - Friesland, Groningen, Z"urich, Bern, Basel, Geneva, d708 1 a708 1 1760-1812 - Graub"unden d762 6 @ 1.14.4.1 log @Pull up the following revisions via patch, requested by apb in ticket #453: doc/3RDPARTY up to 1.1195 usr.sbin/zdump/Makefile up to 1.9 usr.sbin/zic/Makefile up to 1.15 lib/libc/time/Makefile up to 1.25 lib/libc/time/Makefile.inc up to 1.21 lib/libc/time/NEWS up to 1.8 lib/libc/time/README up to 1.9 lib/libc/time/Theory up to 1.16 lib/libc/time/asctime.c up to 1.20 lib/libc/time/checktab.awk up to 1.8 lib/libc/time/ctime.3 up to 1.51 lib/libc/time/getdate.c up to 1.3 lib/libc/time/localtime.c up to 1.92 lib/libc/time/private.h up to 1.38 lib/libc/time/strftime.c up to 1.33 lib/libc/time/time2posix.3 up to 1.19 lib/libc/time/tz-art.htm up to 1.8 lib/libc/time/tz-link.htm up to 1.20 lib/libc/time/tzfile.5 up to 1.22 lib/libc/time/tzfile.h up to 1.16 lib/libc/time/tzselect.8 up to 1.6 lib/libc/time/tzselect.ksh up to 1.12 lib/libc/time/tzset.3 up to 1.31 lib/libc/time/zdump.8 up to 1.14 lib/libc/time/zdump.c up to 1.40 lib/libc/time/zic.8 up to 1.24 lib/libc/time/zic.c up to 1.52 Update tzcode from 2014e to 2014j. @ text @d90 1 a90 1 applications that an administrator wants used only at certain times - d94 1 a94 1 daylight saving time shifts - as might be required to limit phone d99 1 a99 1 * The tz code attempts to support all the time_t implementations d106 1 a106 1 and 36-bit and 40-bit integers are also used occasionally. d130 1 a130 1 to continue using "TZ": it is widely used for time zone purposes; d159 1 a159 1 used if tzset is called - directly or indirectly - and there's no "TZ" d197 1 a197 1 not in any sense "standard compatible" - some are not, in fact, specified in d226 1 a226 1 could misbehave if data entries were omitted for pre-1970 transitions. d236 3 a238 3 Corrections are welcome and encouraged; see the file CONTRIBUTING. Users requiring authoritative data should consult national standards bodies and the references cited in the database's comments. d249 1 a249 1 * The pre-1970 entries in this database cover only a tiny sliver of how d257 1 a257 1 * Most of the pre-1970 data entries come from unreliable sources, often d262 1 a262 1 and on the rare occasions when they are checked they are d285 2 a286 2 * The tz database does not record the earliest time for which a zone's data entries are thereafter valid for every location in the region. d321 1 a321 1 * The tz database models pre-standard time using the proleptic Gregorian d327 2 a328 2 * Early clocks were less reliable, and data entries do not represent this unreliability. d348 1 a348 1 Ideally it would contain information about when data entries are d408 1 a408 2 to 'Bandar_Seri_Begawan'. Exceptions: see the discussion of legacy names below. d427 1 a427 1 e.g. many cities are named San José and Georgetown, so d434 1 a434 1 prefer 'Athens' to the Greek 'Αθήνα' or the Romanized 'Athína'. d457 1 a457 1 The file 'zone1970.tab' lists geographical locations used to name time d460 1 a460 1 names in the data. Although a 'zone1970.tab' location's longitude d467 2 a468 1 (e.g., 'US/Eastern' instead of 'America/New_York'). a471 12 Older versions of this package defined legacy names that are incompatible with the first rule of location names, but which are still supported. These legacy names are mostly defined in the file 'etcetera'. Also, the file 'backward' defines the legacy names 'GMT0', 'GMT-0', 'GMT+0' and 'Canada/East-Saskatchewan', and the file 'northamerica' defines the legacy names 'EST5EDT', 'CST6CDT', 'MST7MDT', and 'PST8PDT'. Excluding 'backward' should not affect the other data. If 'backward' is excluded, excluding 'etcetera' should not affect the remaining data. d533 1 a533 1 in practice: e.g. 'CST' has a different meaning in China than d535 2 a536 2 to use numeric UT offsets like '-0600' instead of time zone abbreviations like 'CST'; this avoids the ambiguity. d545 4 a548 3 Calendrical Calculations: Third Edition, Cambridge University Press (2008) . Other information and sources are given below. They sometimes disagree. d577 1 a577 1 If your source is correct, how come documents between 1929 and 1940 were d589 3 a591 2 Subject: Re: Gregorian reform - a part of locale? d597 1 a597 1 year after 1696 would be in 1744 - putting the whole country on a calendar d609 3 a611 3 produced the following references to support it: "Tideräkning och historia" by Natanael Beckman (1924) and "Tid, en bok om tideräkning och kalenderväsen" by Lars-Olof Lodén (1968). d632 1 a632 1 10/21 Feb 1583 - bishopric of Liege (Lüttich) d637 1 a637 1 13/24 Oct 1583 - Austrian Oberelsaß and Breisgau d639 3 a641 3 02/13 Nov 1583 - duchy of Jülich-Berg 02/13 Nov 1583 - electorate and city of Köln 04/15 Nov 1583 - bishopric of Würzburg d644 1 a644 1 17/28 Nov 1583 - bishopric of Münster and duchy of Cleve d648 1 a648 1 11/22 Jan 1584 - Lucerne, Uri, Schwyz, Zug, Freiburg, Solothurn d667 1 a667 1 1624 - bishopric of Osnabrück d686 1 a686 1 12 Jan 1701 - Friesland, Groningen, Zürich, Bern, Basel, Geneva, d698 1 a698 1 1760-1812 - Graubünden d703 1 a703 1 Source: H. Grotefend, _Taschenbuch der Zeitrechnung des deutschen d705 1 a705 1 (Hannover: Hahnsche Buchhandlung, 1941), pp. 26-28. a751 6 ----- Local Variables: coding: utf-8 End: @ 1.13 log @welcome to 2013d @ text @d15 1 a15 1 These time and date functions are upwards compatible with POSIX, d19 3 a21 6 Standard for Information technology -- Portable Operating System Interface (POSIX (R)) -- System Interfaces IEEE Std 1003.1, 2004 Edition d34 1 a34 1 stdoffset[dst[offset],date[/time],date[/time]] d45 3 a47 3 is of the form `[-]hh:[mm[:ss]]' and specifies the offset west of UTC. The default DST offset is one hour ahead of standard time. d53 3 a55 1 takes the form `hh:[mm[:ss]]' and defaults to 02:00. d65 1 a65 1 and `5' stands for the last week in which day d appears d67 2 d99 13 d163 2 d174 1 a174 1 `zic' supplied with this package instead of using the system `zic', d192 1 a192 1 time_t values when doing conversions for places that don't use UTC. d219 4 a222 1 with a notable location. d232 4 a235 2 As noted in the README file, the tz database is not authoritative (particularly not for pre-1970 time stamps), and it surely has errors. d240 120 d395 2 a396 2 area, `America'. Typical names are `Africa/Cairo', `America/New_York', and `Pacific/Honolulu'. d402 3 a404 2 names other than `/'). Within a file name component, use only ASCII letters, `.', `-' and `_'. Do not use d407 3 a409 2 characters or start with `-'. E.g., prefer `Brunei' to `Bandar_Seri_Begawan'. d411 1 a411 1 implementation is case-sensitive, some other implementations d413 4 d419 3 d428 1 a428 1 prefer `Costa_Rica' to `San_Jose' and `Guyana' to `Georgetown'. d431 4 a434 4 locations into different time zones. E.g. prefer `Paris' to `France', since France has had multiple time zones. Use mainstream English spelling, e.g. prefer `Rome' to `Roma', and prefer `Athens' to the true name (which uses Greek letters). d437 1 a437 1 e.g. prefer `Shanghai' to `Beijing'. Among locations with d439 6 a444 6 e.g. prefer `Rome' to `Milan'. Use the singular form, e.g. prefer `Canary' to `Canaries'. Omit common suffixes like `_Islands' and `_City', unless that would lead to ambiguity. E.g. prefer `Cayman' to `Cayman_Islands' and `Guatemala' to `Guatemala_City', but prefer `Mexico_City' to `Mexico' because the country d446 3 a448 3 Use `_' to represent a space. Omit `.' from abbreviations in names, e.g. prefer `St_Helena' to `St._Helena'. d451 1 a451 1 the existing name `Rome' to `Milan' merely because d454 1 a454 1 If a name is changed, put its old spelling in the `backward' file. d457 6 a462 3 The file `zone.tab' lists the geographical locations used to name time zone rule files. It is intended to be an exhaustive list of names for geographic regions as described above. d466 3 a468 2 See the file `backward' for most of these older names (e.g. `US/Eastern' instead of `America/New_York'). d470 1 a470 1 `WET', `CET', `MET', and `EET' (see the file `europe'). d476 1 a476 1 like `EST' to be compatible with human tradition and POSIX. d503 1 a503 1 e.g. `EST' for Eastern Standard Time in North America. d506 1 a506 1 a French application might translate `EST' to `HNE'. d509 2 a510 2 traditional xMT notation, e.g. `PMT' for Paris Mean Time. The only name like this in current use is `GMT'. d515 1 a515 1 (e.g. ``Cape Verde Time''), then: d518 3 a520 3 append `T' to the country's ISO code, e.g. `CVT' for Cape Verde Time. For summer time append `ST'; for double summer time append `DST'; etc. d525 5 a529 2 Use UTC (with time zone abbreviation "zzz") for locations while uninhabited. The "zzz" mnemonic is that these locations are, d533 1 a533 1 in practice: e.g. `EST' has a different meaning in Australia than d535 2 a536 2 to use numeric UTC offsets like `-0500' instead of time zone abbreviations like `EST'; this avoids the ambiguity. d561 1 a561 1 On 1929-10-01 the Soviet Union instituted an ``Eternal Calendar'' @ 1.12 log @welcome to tzcode2012h via patch. @ text @d267 4 a270 4 Include at least one location per time zone rule set per country. One such location is enough. Use ISO 3166 (see the file iso3166.tab) to help decide whether something is a country. However, uninhabited ISO 3166 regions like Bouvet Island d272 1 a272 1 If all the clocks in a country's region have agreed since 1970, d286 1 a286 1 Use the most populous among locations in a country's time zone, d305 1 d309 1 a309 1 of canonical names for geographic regions. d363 1 a363 1 When a country has a single or principal time zone region, d367 3 a369 4 When a country has multiple time zones, take the first three letters of an English place name identifying each zone and then append `T', `ST', etc. as before; e.g. `VLAST' for VLAdivostok Summer Time. d590 1 a590 1 (2004-07-30). d593 1 @ 1.12.2.1 log @sync with HEAD @ text @d267 4 a270 4 Do not use names that differ only in case. Although the reference implementation is case-sensitive, some other implementations are not, and they would mishandle names differing only in case. Uninhabited regions like the North Pole and Bouvet Island d272 1 a272 1 If all the clocks in a region have agreed since 1970, d286 1 a286 1 Use the most populous among locations in a zone, a304 1 This means old spellings will continue to work. d308 1 a308 1 of names for geographic regions as described above. d362 1 a362 1 When a country is identified with a single or principal zone, d366 4 a369 3 Otherwise, take the first three letters of an English place name identifying each zone and append 'T', 'ST', etc. as before; e.g. 'VLAST' for VLAdivostok Summer Time. d590 1 a590 1 (2012-08-08). a592 1 @ 1.11 log @merge 2012e @ text @d229 1 a229 1 * Indicate to humans as to where that region is. This simplifes use. @ 1.11.2.1 log @Resync to 2012-11-19 00:00:00 UTC @ text @d229 1 a229 1 * Indicate to humans as to where that region is. This simplifies use. @ 1.11.2.2 log @Rebase to HEAD as of a few days ago. @ text @d15 1 a15 1 These time and date functions are upwards compatible with those of POSIX, d19 6 a24 3 The Open Group Base Specifications Issue 7 IEEE Std 1003.1, 2013 Edition d37 1 a37 1 stdoffset[dst[offset][,date[/time],date[/time]]] d48 3 a50 3 is of the form '[+-]hh:[mm[:ss]]' and specifies the offset west of UT. 'hh' may be a single digit; 0<=hh<=24. The default DST offset is one hour ahead of standard time. d56 1 a56 3 takes the form 'hh:[mm[:ss]]' and defaults to 02:00. This is the same format as the offset, except that a leading '+' or '-' is not allowed. d66 1 a66 1 and '5' stands for the last week in which day d appears a67 2 Typically, this is the only useful form; the n and Jn forms are rarely used. a97 13 * The tz code attempts attempts to support all the time_t implementations allowed by POSIX. The time_t type represents a nonnegative count of seconds since 1970-01-01 00:00:00 UTC, ignoring leap seconds. In practice, time_t is usually a signed 64- or 32-bit integer; 32-bit signed time_t values stop working after 2038-01-19 03:14:07 UTC, so new implementations these days typically use a signed 64-bit integer. Unsigned 32-bit integers are used on one or two platforms, and 36-bit integers are also used occasionally. Although earlier POSIX versions allowed time_t to be a floating-point type, this was not supported by any practical systems, and POSIX.1-2013 and the tz code both require time_t to be an integer type. a148 2 * Negative time_t values are supported, on systems where time_t is signed. d158 1 a158 1 'zic' supplied with this package instead of using the system 'zic', d176 1 a176 1 time_t values when doing conversions for places that don't use UT. d203 1 a203 4 with a notable location. Although 1970 is a somewhat-arbitrary cutoff, there are significant challenges to moving the cutoff earlier even by a decade or two, due to the wide variety of local practices before computer timekeeping became prevalent. d213 2 a214 4 ----- Accuracy of the tz database ----- The tz database is not authoritative, and it surely has errors. a218 120 Errors in the tz database arise from many sources: * The tz database predicts future time stamps, and current predictions will be incorrect after future governments change the rules. For example, if today someone schedules a meeting for 13:00 next October 1, Casablanca time, and tomorrow Morocco changes its daylight saving rules, software can mess up after the rule change if it blithely relies on conversions made before the change. * The pre-1970 data in this database cover only a tiny sliver of how clocks actually behaved; the vast majority of the necessary information was lost or never recorded. Thousands more zones would be needed if the tz database's scope were extended to cover even just the known or guessed history of standard time; for example, the current single entry for France would need to split into dozens of entries, perhaps hundreds. * Most of the pre-1970 data comes from unreliable sources, often astrology books that lack citations and whose compilers evidently invented entries when the true facts were unknown, without reporting which entries were known and which were invented. These books often contradict each other or give implausible entries, and on the rare occasions when their old data are checked they are typically found to be incorrect. * For the UK the tz database relies on years of first-class work done by Joseph Myers and others; see . Other countries are not done nearly as well. * Sometimes, different people in the same city would maintain clocks that differed significantly. Railway time was used by railroad companies (which did not always agree with each other), church-clock time was used for birth certificates, etc. Often this was merely common practice, but sometimes it was set by law. For example, from 1891 to 1911 the UT offset in France was legally 0:09:21 outside train stations and 0:04:21 inside. * Although a named location in the tz database stands for the containing region, its pre-1970 data entries are often accurate for only a small subset of that region. For example, Europe/London stands for the United Kingdom, but its pre-1847 times are valid only for locations that have London's exact meridian, and its 1847 transition to GMT is known to be valid only for the L&NW and the Caledonian railways. * The tz database does not record the earliest time for which a zone's data is thereafter valid for every location in the region. For example, Europe/London is valid for all locations in its region after GMT was made the standard time, but the date of standardization (1880-08-02) is not in the tz database, other than in commentary. For many zones the earliest time of validity is unknown. * The tz database does not record a region's boundaries, and in many cases the boundaries are not known. For example, the zone America/Kentucky/Louisville represents a region around the city of Louisville, the boundaries of which are unclear. * Changes that are modeled as instantaneous transitions in the tz database were often spread out over hours, days, or even decades. * Even if the time is specified by law, locations sometimes deliberately flout the law. * Early timekeeping practices, even assuming perfect clocks, were often not specified to the accuracy that the tz database requires. * Sometimes historical timekeeping was specified more precisely than what the tz database can handle. For example, from 1909 to 1937 Netherlands clocks were legally UT+00:19:32.13, but the tz database cannot represent the fractional second. * Even when all the timestamp transitions recorded by the tz database are correct, the tz rules that generate them may not faithfully reflect the historical rules. For example, from 1922 until World War II the UK moved clocks forward the day following the third Saturday in April unless that was Easter, in which case it moved clocks forward the previous Sunday. Because the tz database has no way to specify Easter, these exceptional years are entered as separate tz Rule lines, even though the legal rules did not change. * The tz database models pre-standard time using the Gregorian calendar and local mean time (LMT), but many people used other calendars and other timescales. For example, the Roman Empire used the Julian calendar, and had 12 varying-length daytime hours with a non-hour-based system at night. * Early clocks were less reliable, and the data do not represent this unreliability. * As for leap seconds, civil time was not based on atomic time before 1972, and we don't know the history of earth's rotation accurately enough to map SI seconds to historical solar time to more than about one-hour accuracy. See: Morrison LV, Stephenson FR. Historical values of the Earth's clock error Delta T and the calculation of eclipses. J Hist Astron. 2004;35:327-36 ; Historical values of the Earth's clock error. J Hist Astron. 2005;36:339 . * The relationship between POSIX time (that is, UTC but ignoring leap seconds) and UTC is not agreed upon after 1972. Although the POSIX clock officially stops during an inserted leap second, at least one proposed standard has it jumping back a second instead; and in practice POSIX clocks more typically either progress glacially during a leap second, or are slightly slowed while near a leap second. * The tz database does not represent how uncertain its information is. Ideally it would contain information about when the data are incomplete or dicey. Partial temporal knowledge is a field of active research, though, and it's not clear how to apply it here. In short, many, perhaps most, of the tz database's pre-1970 and future time stamps are either wrong or misleading. Any attempt to pass the tz database off as the definition of time should be unacceptable to anybody who cares about the facts. In particular, the tz database's LMT offsets should not be considered meaningful, and should not prompt creation of zones merely because two locations differ in LMT or transitioned to standard time at different dates. d254 2 a255 2 area, 'America'. Typical names are 'Africa/Cairo', 'America/New_York', and 'Pacific/Honolulu'. d261 2 a262 3 names other than '/'). Do not use the file name components '.' and '..'. Within a file name component, use only ASCII letters, '.', '-' and '_'. Do not use d265 6 a270 11 characters or start with '-'. E.g., prefer 'Brunei' to 'Bandar_Seri_Begawan'. A name must not be empty, or contain '//', or start or end with '/'. Do not use names that differ only in case. Although the reference implementation is case-sensitive, some other implementations are not, and they would mishandle names differing only in case. If one name A is an initial prefix of another name AB (ignoring case), then B must not start with '/', as a regular file cannot have the same name as a directory in POSIX. For example, 'America/New_York' precludes 'America/New_York/Bronx'. Uninhabited regions like the North Pole and Bouvet Island d272 1 a272 4 There should typically be at least one name for each ISO 3166-1 officially assigned two-letter code for an inhabited country or territory. If all the clocks in a region have agreed since 1970, d278 1 a278 1 prefer 'Costa_Rica' to 'San_Jose' and 'Guyana' to 'Georgetown'. d281 4 a284 4 locations into different time zones. E.g. prefer 'Paris' to 'France', since France has had multiple time zones. Use mainstream English spelling, e.g. prefer 'Rome' to 'Roma', and prefer 'Athens' to the true name (which uses Greek letters). d286 2 a287 2 Use the most populous among locations in a zone, e.g. prefer 'Shanghai' to 'Beijing'. Among locations with d289 6 a294 6 e.g. prefer 'Rome' to 'Milan'. Use the singular form, e.g. prefer 'Canary' to 'Canaries'. Omit common suffixes like '_Islands' and '_City', unless that would lead to ambiguity. E.g. prefer 'Cayman' to 'Cayman_Islands' and 'Guatemala' to 'Guatemala_City', but prefer 'Mexico_City' to 'Mexico' because the country d296 3 a298 3 Use '_' to represent a space. Omit '.' from abbreviations in names, e.g. prefer 'St_Helena' to 'St._Helena'. d301 1 a301 1 the existing name 'Rome' to 'Milan' merely because d304 1 a304 2 If a name is changed, put its old spelling in the 'backward' file. This means old spellings will continue to work. d306 3 a308 6 The file 'zone.tab' lists geographical locations used to name time zone rule files. It is intended to be an exhaustive list of names for geographic regions as described above; this is a subset of the names in the data. Although a 'zone.tab' location's longitude corresponds to its LMT offset with one hour for every 15 degrees east longitude, this relationship is not exact. d312 2 a313 3 See the file 'backward' for most of these older names (e.g. 'US/Eastern' instead of 'America/New_York'); excluding 'backward' should not affect the other data. d315 1 a315 1 'WET', 'CET', 'MET', and 'EET' (see the file 'europe'). d321 1 a321 1 like 'EST' to be compatible with human tradition and POSIX. d348 1 a348 1 e.g. 'EST' for Eastern Standard Time in North America. d351 1 a351 1 a French application might translate 'EST' to 'HNE'. d354 2 a355 2 traditional xMT notation, e.g. 'PMT' for Paris Mean Time. The only name like this in current use is 'GMT'. d360 1 a360 9 (e.g. "Cape Verde Time"), then: When a country is identified with a single or principal zone, append 'T' to the country's ISO code, e.g. 'CVT' for Cape Verde Time. For summer time append 'ST'; for double summer time append 'DST'; etc. Otherwise, take the first three letters of an English place name identifying each zone and append 'T', 'ST', etc. as before; e.g. 'VLAST' for VLAdivostok Summer Time. d362 8 a369 2 Use 'LMT' for local mean time of locations before the introduction of standard time; see "Scope of the tz database". d371 2 a372 2 Use UT (with time zone abbreviation 'zzz') for locations while uninhabited. The 'zzz' mnemonic is that these locations are, d376 1 a376 1 in practice: e.g. 'EST' has a different meaning in Australia than d378 2 a379 2 to use numeric UT offsets like '-0500' instead of time zone abbreviations like 'EST'; this avoids the ambiguity. d404 1 a404 1 On 1929-10-01 the Soviet Union instituted an "Eternal Calendar" d590 1 a590 1 (2012-08-08). a592 1 @ 1.10 log @bring in the 2011i changes. @ text @a0 2 # $NetBSD: Theory,v 1.9 2009/12/31 22:49:15 mlelstv Exp $ @@(#)Theory 8.6 d197 6 a202 6 The tz database attempts to record the history and predicted future of all computer-based clocks that track civil time. To represent this data, the world is partitioned into regions whose clocks all agree about time stamps that occur after the somewhat-arbitrary cutoff point of the POSIX Epoch (1970-01-01 00:00:00 UTC). For each such region, the database records all known clock transitions, and labels the region d205 2 a206 2 Clock transitions before 1970 are recorded for each such location, because most POSIX-compatible systems support negative time stamps and d208 3 a210 3 However, the database is not designed for and does not suffice for applications requiring accurate handling of all past times everywhere, as it would take far too much effort and guesswork to record all d213 1 a213 1 As noted in the README file, the tz database is not authoritative d215 2 a216 2 Corrections are welcome and encouraged. Users requiring authoritative data should consult national standards bodies and the references cited d315 1 a315 1 +`WET', `CET', `MET', and `EET' (see the file `europe'). @ 1.10.2.1 log @sync with head @ text @d1 2 d199 6 a204 6 The tz database attempts to record the history and predicted future of all computer-based clocks that track civil time. To represent this data, the world is partitioned into regions whose clocks all agree about time stamps that occur after the somewhat-arbitrary cutoff point of the POSIX Epoch (1970-01-01 00:00:00 UTC). For each such region, the database records all known clock transitions, and labels the region d207 2 a208 2 Clock transitions before 1970 are recorded for each such location, because most POSIX-compatible systems support negative time stamps and d210 3 a212 3 However, the database is not designed for and does not suffice for applications requiring accurate handling of all past times everywhere, as it would take far too much effort and guesswork to record all d215 1 a215 1 As noted in the README file, the tz database is not authoritative d217 2 a218 2 Corrections are welcome and encouraged. Users requiring authoritative data should consult national standards bodies and the references cited d231 1 a231 1 * Indicate to humans as to where that region is. This simplifies use. d317 1 a317 1 `WET', `CET', `MET', and `EET' (see the file `europe'). @ 1.10.2.2 log @sync with head. for a reference, the tree before this commit was tagged as yamt-pagecache-tag8. this commit was splitted into small chunks to avoid a limitation of cvs. ("Protocol error: too many arguments") @ text @d15 1 a15 1 These time and date functions are upwards compatible with those of POSIX, d19 6 a24 3 The Open Group Base Specifications Issue 7 IEEE Std 1003.1, 2013 Edition d37 1 a37 1 stdoffset[dst[offset][,date[/time],date[/time]]] d48 3 a50 3 is of the form '[+-]hh:[mm[:ss]]' and specifies the offset west of UT. 'hh' may be a single digit; 0<=hh<=24. The default DST offset is one hour ahead of standard time. d56 1 a56 3 takes the form 'hh:[mm[:ss]]' and defaults to 02:00. This is the same format as the offset, except that a leading '+' or '-' is not allowed. d66 1 a66 1 and '5' stands for the last week in which day d appears a67 2 Typically, this is the only useful form; the n and Jn forms are rarely used. a97 13 * The tz code attempts attempts to support all the time_t implementations allowed by POSIX. The time_t type represents a nonnegative count of seconds since 1970-01-01 00:00:00 UTC, ignoring leap seconds. In practice, time_t is usually a signed 64- or 32-bit integer; 32-bit signed time_t values stop working after 2038-01-19 03:14:07 UTC, so new implementations these days typically use a signed 64-bit integer. Unsigned 32-bit integers are used on one or two platforms, and 36-bit integers are also used occasionally. Although earlier POSIX versions allowed time_t to be a floating-point type, this was not supported by any practical systems, and POSIX.1-2013 and the tz code both require time_t to be an integer type. a148 2 * Negative time_t values are supported, on systems where time_t is signed. d158 1 a158 1 'zic' supplied with this package instead of using the system 'zic', d176 1 a176 1 time_t values when doing conversions for places that don't use UT. d203 1 a203 4 with a notable location. Although 1970 is a somewhat-arbitrary cutoff, there are significant challenges to moving the cutoff earlier even by a decade or two, due to the wide variety of local practices before computer timekeeping became prevalent. d213 2 a214 4 ----- Accuracy of the tz database ----- The tz database is not authoritative, and it surely has errors. a218 120 Errors in the tz database arise from many sources: * The tz database predicts future time stamps, and current predictions will be incorrect after future governments change the rules. For example, if today someone schedules a meeting for 13:00 next October 1, Casablanca time, and tomorrow Morocco changes its daylight saving rules, software can mess up after the rule change if it blithely relies on conversions made before the change. * The pre-1970 data in this database cover only a tiny sliver of how clocks actually behaved; the vast majority of the necessary information was lost or never recorded. Thousands more zones would be needed if the tz database's scope were extended to cover even just the known or guessed history of standard time; for example, the current single entry for France would need to split into dozens of entries, perhaps hundreds. * Most of the pre-1970 data comes from unreliable sources, often astrology books that lack citations and whose compilers evidently invented entries when the true facts were unknown, without reporting which entries were known and which were invented. These books often contradict each other or give implausible entries, and on the rare occasions when their old data are checked they are typically found to be incorrect. * For the UK the tz database relies on years of first-class work done by Joseph Myers and others; see . Other countries are not done nearly as well. * Sometimes, different people in the same city would maintain clocks that differed significantly. Railway time was used by railroad companies (which did not always agree with each other), church-clock time was used for birth certificates, etc. Often this was merely common practice, but sometimes it was set by law. For example, from 1891 to 1911 the UT offset in France was legally 0:09:21 outside train stations and 0:04:21 inside. * Although a named location in the tz database stands for the containing region, its pre-1970 data entries are often accurate for only a small subset of that region. For example, Europe/London stands for the United Kingdom, but its pre-1847 times are valid only for locations that have London's exact meridian, and its 1847 transition to GMT is known to be valid only for the L&NW and the Caledonian railways. * The tz database does not record the earliest time for which a zone's data is thereafter valid for every location in the region. For example, Europe/London is valid for all locations in its region after GMT was made the standard time, but the date of standardization (1880-08-02) is not in the tz database, other than in commentary. For many zones the earliest time of validity is unknown. * The tz database does not record a region's boundaries, and in many cases the boundaries are not known. For example, the zone America/Kentucky/Louisville represents a region around the city of Louisville, the boundaries of which are unclear. * Changes that are modeled as instantaneous transitions in the tz database were often spread out over hours, days, or even decades. * Even if the time is specified by law, locations sometimes deliberately flout the law. * Early timekeeping practices, even assuming perfect clocks, were often not specified to the accuracy that the tz database requires. * Sometimes historical timekeeping was specified more precisely than what the tz database can handle. For example, from 1909 to 1937 Netherlands clocks were legally UT+00:19:32.13, but the tz database cannot represent the fractional second. * Even when all the timestamp transitions recorded by the tz database are correct, the tz rules that generate them may not faithfully reflect the historical rules. For example, from 1922 until World War II the UK moved clocks forward the day following the third Saturday in April unless that was Easter, in which case it moved clocks forward the previous Sunday. Because the tz database has no way to specify Easter, these exceptional years are entered as separate tz Rule lines, even though the legal rules did not change. * The tz database models pre-standard time using the Gregorian calendar and local mean time (LMT), but many people used other calendars and other timescales. For example, the Roman Empire used the Julian calendar, and had 12 varying-length daytime hours with a non-hour-based system at night. * Early clocks were less reliable, and the data do not represent this unreliability. * As for leap seconds, civil time was not based on atomic time before 1972, and we don't know the history of earth's rotation accurately enough to map SI seconds to historical solar time to more than about one-hour accuracy. See: Morrison LV, Stephenson FR. Historical values of the Earth's clock error Delta T and the calculation of eclipses. J Hist Astron. 2004;35:327-36 ; Historical values of the Earth's clock error. J Hist Astron. 2005;36:339 . * The relationship between POSIX time (that is, UTC but ignoring leap seconds) and UTC is not agreed upon after 1972. Although the POSIX clock officially stops during an inserted leap second, at least one proposed standard has it jumping back a second instead; and in practice POSIX clocks more typically either progress glacially during a leap second, or are slightly slowed while near a leap second. * The tz database does not represent how uncertain its information is. Ideally it would contain information about when the data are incomplete or dicey. Partial temporal knowledge is a field of active research, though, and it's not clear how to apply it here. In short, many, perhaps most, of the tz database's pre-1970 and future time stamps are either wrong or misleading. Any attempt to pass the tz database off as the definition of time should be unacceptable to anybody who cares about the facts. In particular, the tz database's LMT offsets should not be considered meaningful, and should not prompt creation of zones merely because two locations differ in LMT or transitioned to standard time at different dates. d254 2 a255 2 area, 'America'. Typical names are 'Africa/Cairo', 'America/New_York', and 'Pacific/Honolulu'. d261 2 a262 3 names other than '/'). Do not use the file name components '.' and '..'. Within a file name component, use only ASCII letters, '.', '-' and '_'. Do not use d265 6 a270 11 characters or start with '-'. E.g., prefer 'Brunei' to 'Bandar_Seri_Begawan'. A name must not be empty, or contain '//', or start or end with '/'. Do not use names that differ only in case. Although the reference implementation is case-sensitive, some other implementations are not, and they would mishandle names differing only in case. If one name A is an initial prefix of another name AB (ignoring case), then B must not start with '/', as a regular file cannot have the same name as a directory in POSIX. For example, 'America/New_York' precludes 'America/New_York/Bronx'. Uninhabited regions like the North Pole and Bouvet Island d272 1 a272 4 There should typically be at least one name for each ISO 3166-1 officially assigned two-letter code for an inhabited country or territory. If all the clocks in a region have agreed since 1970, d278 1 a278 1 prefer 'Costa_Rica' to 'San_Jose' and 'Guyana' to 'Georgetown'. d281 4 a284 4 locations into different time zones. E.g. prefer 'Paris' to 'France', since France has had multiple time zones. Use mainstream English spelling, e.g. prefer 'Rome' to 'Roma', and prefer 'Athens' to the true name (which uses Greek letters). d286 2 a287 2 Use the most populous among locations in a zone, e.g. prefer 'Shanghai' to 'Beijing'. Among locations with d289 6 a294 6 e.g. prefer 'Rome' to 'Milan'. Use the singular form, e.g. prefer 'Canary' to 'Canaries'. Omit common suffixes like '_Islands' and '_City', unless that would lead to ambiguity. E.g. prefer 'Cayman' to 'Cayman_Islands' and 'Guatemala' to 'Guatemala_City', but prefer 'Mexico_City' to 'Mexico' because the country d296 3 a298 3 Use '_' to represent a space. Omit '.' from abbreviations in names, e.g. prefer 'St_Helena' to 'St._Helena'. d301 1 a301 1 the existing name 'Rome' to 'Milan' merely because d304 1 a304 2 If a name is changed, put its old spelling in the 'backward' file. This means old spellings will continue to work. d306 3 a308 6 The file 'zone.tab' lists geographical locations used to name time zone rule files. It is intended to be an exhaustive list of names for geographic regions as described above; this is a subset of the names in the data. Although a 'zone.tab' location's longitude corresponds to its LMT offset with one hour for every 15 degrees east longitude, this relationship is not exact. d312 2 a313 3 See the file 'backward' for most of these older names (e.g. 'US/Eastern' instead of 'America/New_York'); excluding 'backward' should not affect the other data. d315 1 a315 1 'WET', 'CET', 'MET', and 'EET' (see the file 'europe'). d321 1 a321 1 like 'EST' to be compatible with human tradition and POSIX. d348 1 a348 1 e.g. 'EST' for Eastern Standard Time in North America. d351 1 a351 1 a French application might translate 'EST' to 'HNE'. d354 2 a355 2 traditional xMT notation, e.g. 'PMT' for Paris Mean Time. The only name like this in current use is 'GMT'. d360 1 a360 9 (e.g. "Cape Verde Time"), then: When a country is identified with a single or principal zone, append 'T' to the country's ISO code, e.g. 'CVT' for Cape Verde Time. For summer time append 'ST'; for double summer time append 'DST'; etc. Otherwise, take the first three letters of an English place name identifying each zone and append 'T', 'ST', etc. as before; e.g. 'VLAST' for VLAdivostok Summer Time. d362 8 a369 2 Use 'LMT' for local mean time of locations before the introduction of standard time; see "Scope of the tz database". d371 2 a372 2 Use UT (with time zone abbreviation 'zzz') for locations while uninhabited. The 'zzz' mnemonic is that these locations are, d376 1 a376 1 in practice: e.g. 'EST' has a different meaning in Australia than d378 2 a379 2 to use numeric UT offsets like '-0500' instead of time zone abbreviations like 'EST'; this avoids the ambiguity. d404 1 a404 1 On 1929-10-01 the Soviet Union instituted an "Eternal Calendar" d590 1 a590 1 (2012-08-08). a592 1 @ 1.9 log @Import tzcode2009k. - now understands 64bit time_t and 64bit data in timezone files. - localtime(), gmtime(), asctime() and ctime() may now fail with a NULL result if time_t cannot be represented by struct tm. @ text @d1 2 a2 2 # $NetBSD: Theory,v 1.8 2004/05/27 20:39:49 kleink Exp $ @@(#)Theory 8.3 d9 2 a10 1 Names of time zone regions d197 25 d317 1 a317 2 `WET', `CET', `MET', `EET' (see the file `europe'), and `Factory' (see the file `factory'). d389 4 a392 4 resource in this area is Edward M. Reingold and Nachum Dershowitz, Calendrical Calculations: The Millennium Edition , Cambridge University Press (2001). Other information and @ 1.8 log @Merge tzcode2004a. @ text @d1 4 a4 3 # $NetBSD: Theory,v 1.7 2003/12/20 00:12:05 kleink Exp $ @@(#)Theory 7.15 a13 1 d16 1 a16 1 These time and date functions are upwards compatible with POSIX.1, d18 1 a18 1 As of this writing, the current edition of POSIX.1 is: d20 6 a25 5 Information technology --Portable Operating System Interface (POSIX (R)) -- Part 1: System Application Program Interface (API) [C Language] ISO/IEC 9945-1:1996 ANSI/IEEE Std 1003.1, 1996 Edition 1996-07-12 d27 1 a27 1 POSIX.1 has the following properties and limitations. d29 2 a30 2 * In POSIX.1, time display in a process is controlled by the environment variable TZ. Unfortunately, the POSIX.1 TZ string takes d32 1 a32 1 Also, POSIX.1 TZ strings can't deal with other (for example, Israeli) d36 1 a36 1 The POSIX.1 TZ string takes the following form: d45 3 d70 13 a82 2 * In POSIX.1, when a TZ value like "EST5EDT" is parsed, typically the current US DST rules are used, d88 1 a88 1 * In POSIX.1, there's no tamper-proof way for a process to learn the d97 1 a97 1 * POSIX.1 requires that systems ignore leap seconds. d99 1 a99 1 These are the extensions that have been made to the POSIX.1 functions: d127 1 a127 1 abbreviation to be used. This differs from POSIX.1, where the elements d150 1 a150 2 * These functions can account for leap seconds, thanks to Bradley White (bww@@k.cs.cmu.edu). d191 3 a193 3 contain valid extensions to POSIX.1, to ensure its broad acceptability. If more powerful time conversion functions can be standardized, so much the better. d246 2 d283 2 a284 1 time zone rule files. d298 1 a298 1 like `EST' to be compatible with human tradition and POSIX.1. d313 1 a313 1 been specified by a POSIX.1 TZ string. POSIX.1 d315 1 a315 1 abbreviation. POSIX.1-1996 says that an abbreviation d317 4 a320 4 '+', NUL, or a digit. Draft 7 of POSIX 1003.1-200x changes this rule to say that an abbreviation can contain only '-', '+', and alphanumeric characters in the current locale. To be portable to both sets of d322 1 a322 2 letters, as these are the only letters that are alphabetic in all locales. d348 3 a350 2 Use "zzz" for locations while uninhabited. The mnemonic is that these locations are, in some sense, asleep. d364 4 a367 4 resource in this area is Nachum Dershowitz and Edward M. Reingold, Calendrical Calculations , Cambridge University Press (1997). Other information and d380 1 a380 1 From Chris Carrier <72157.3334@@CompuServe.COM> (1996-12-02): d395 1 a395 1 Message-ID: d408 1 a408 1 From: msb@@sq.com (Mark Brader) d436 1 a436 1 From: "Michael Palmer" [with one obvious typo fixed] d440 1 a440 1 Message-ID: <199902091032.CAA09644@@netcom10.netcom.com> d567 1 a567 1 (2004-03-15). @ 1.7 log @Merge tzcode2003e. @ text @d1 2 a2 2 # $NetBSD: Theory,v 1.6 2002/01/29 12:40:33 kleink Exp $ @@(#)Theory 7.14 d11 1 d509 45 @ 1.7.2.1 log @Pull up revision 1.8 (requested by kleink in ticket #407): Update to tzcode2004a. @ text @d1 2 a2 2 # $NetBSD$ @@(#)Theory 7.15 a10 1 Time and time zones on Mars a507 45 ----- Time and time zones on Mars ----- Some people have adjusted their work schedules to fit Mars time. Dozens of special Mars watches were built for Jet Propulsion Laboratory workers who kept Mars time during the Mars Exploration Rovers mission (2004). These timepieces look like normal Seikos and Citizens but use Mars seconds rather than terrestrial seconds. A Mars solar day is called a "sol" and has a mean period equal to about 24 hours 39 minutes 35.244 seconds in terrestrial time. It is divided into a conventional 24-hour clock, so each Mars second equals about 1.02749125 terrestrial seconds. The prime meridian of Mars goes through the center of the crater Airy-0, named in honor of the British astronomer who built the Greenwich telescope that defines Earth's prime meridian. Mean solar time on the Mars prime meridian is called Mars Coordinated Time (MTC). Each landed mission on Mars has adopted a different reference for solar time keeping, so there is no real standard for Mars time zones. For example, the Mars Exploration Rover project (2004) defined two time zones "Local Solar Time A" and "Local Solar Time B" for its two missions, each zone designed so that its time equals local true solar time at approximately the middle of the nominal mission. Such a "time zone" is not particularly suited for any application other than the mission itself. Many calendars have been proposed for Mars, but none have achieved wide acceptance. Astronomers often use Mars Sol Date (MSD) which is a sequential count of Mars solar days elapsed since about 1873-12-29 12:00 GMT. The tz database does not currently support Mars time, but it is documented here in the hopes that support will be added eventually. Sources: Michael Allison and Robert Schmunk, "Technical Notes on Mars Solar Time as Adopted by the Mars24 Sunclock" (2004-03-15). Jia-Rui Chong, "Workdays Fit for a Martian", Los Angeles Times (2004-01-14), pp A1, A20-A21. @ 1.6 log @Merge tzcode2002b. @ text @d1 2 a2 2 # $NetBSD: Theory,v 1.5 2000/12/12 15:25:41 kleink Exp $ @@(#)Theory 7.13 d16 1 a16 1 an international standard for Unix-like systems. d148 1 a148 1 * The Unix Version 7 "timezone" function is not present in this package; @ 1.5 log @Merge tzcode2000g. @ text @d1 2 a2 2 # $NetBSD: Theory,v 1.4 1999/11/10 20:32:31 kleink Exp $ @@(#)Theory 7.11 d39 1 a39 1 d183 28 a210 5 The names of this package's installed time zone rule files are chosen to help minimize possible future incompatibilities due to political events. Ordinarily, names of countries are not used, to avoid incompatibilities when countries change their name (e.g. Zaire->Congo) or when locations change countries (e.g. Hong Kong from UK colony to China). d221 7 a227 3 Use only valid Posix file names. Use only Ascii letters, digits, `.', `-' and `_'. Do not exceed 14 characters or start with `-'. E.g. prefer `Brunei' to `Bandar_Seri_Begawan'. d242 1 a242 1 Use traditional English spelling, e.g. prefer `Rome' to `Roma', and d244 1 a244 1 The Posix file name restrictions encourage this rule. d284 1 a284 4 Use abbreviations that consist of 3 or more upper-case Ascii letters, except use "___" for locations while uninhabited. Posix.1 requires at least 3 characters, and the restriction to upper-case Ascii letters follows most traditions. d289 18 a306 3 to have unexpected effects. In theory, the character set could be !%./@@A-Z^_a-z{}, but these tables use only upper-case Ascii letters (and "___"). d312 1 d316 1 d331 3 d424 2 a425 2 The following is a(n incomplete) listing, arranged chronologically, of European states, with the date they converted from the Julian to the d502 1 a502 1 The Russian empire (including Finland and the Baltic states) did not d505 2 a506 2 Source: H. Grotefend, _Taschenbuch der Zeitrechnung des deutschen Mittelalters und der Neuzeit_, herausgegeben von Dr. O. Grotefend @ 1.5.2.1 log @Catch up to -current. @ text @d1 2 a2 2 # $NetBSD$ @@(#)Theory 7.13 d39 1 a39 1 d183 5 a187 28 The time zone rule file naming conventions attempt to strike a balance among the following goals: * Uniquely identify every national region where clocks have all agreed since 1970. This is essential for the intended use: static clocks keeping local civil time. * Indicate to humans as to where that region is. This simplifes use. * Be robust in the presence of political changes. This reduces the number of updates and backward-compatibility hacks. For example, names of countries are ordinarily not used, to avoid incompatibilities when countries change their name (e.g. Zaire->Congo) or when locations change countries (e.g. Hong Kong from UK colony to China). * Be portable to a wide variety of implementations. This promotes use of the technology. * Use a consistent naming convention over the entire world. This simplifies both use and maintenance. This naming convention is not intended for use by inexperienced users to select TZ values by themselves (though they can of course examine and reuse existing settings). Distributors should provide documentation and/or a simple selection interface that explains the names; see the 'tzselect' program supplied with this distribution for one example. d198 3 a200 7 Use only valid POSIX file name components (i.e., the parts of names other than `/'). Within a file name component, use only ASCII letters, `.', `-' and `_'. Do not use digits, as that might create an ambiguity with POSIX TZ strings. A file name component must not exceed 14 characters or start with `-'. E.g., prefer `Brunei' to `Bandar_Seri_Begawan'. d215 1 a215 1 Use mainstream English spelling, e.g. prefer `Rome' to `Roma', and d217 1 a217 1 The POSIX file name restrictions encourage this rule. d257 4 a260 1 Use abbreviations that consist of three or more ASCII letters. d265 3 a267 18 to have unexpected effects. Previous editions of this rule required upper-case letters, but the Congressman who introduced Chamorro Standard Time preferred "ChST", so the rule has been relaxed. This rule guarantees that all abbreviations could have been specified by a POSIX.1 TZ string. POSIX.1 requires at least three characters for an abbreviation. POSIX.1-1996 says that an abbreviation cannot start with ':', and cannot contain ',', '-', '+', NUL, or a digit. Draft 7 of POSIX 1003.1-200x changes this rule to say that an abbreviation can contain only '-', '+', and alphanumeric characters in the current locale. To be portable to both sets of rules, an abbreviation must therefore use only ASCII letters, as these are the only letters that are alphabetic in all locales. a272 1 a275 1 a289 3 Use "zzz" for locations while uninhabited. The mnemonic is that these locations are, in some sense, asleep. d380 2 a381 2 The following is a(n incomplete) listing, arranged chronologically, of European states, with the date they converted from the Julian to the d458 1 a458 1 The Russian empire (including Finland and the Baltic states) did not d461 2 a462 2 Source: H. Grotefend, _Taschenbuch der Zeitrechnung des deutschen Mittelalters und der Neuzeit_, herausgegeben von Dr. O. Grotefend @ 1.4 log @Merge tzcode1999h. @ text @d1 2 a2 2 # $NetBSD: Theory,v 1.3 1998/01/22 07:06:57 jtc Exp $ @@(#)Theory 7.9 d202 2 a203 1 One such location is enough. d231 6 d243 1 a243 1 See the file `backwards' for most of these older names @ 1.3 log @sync with tzcode1998a @ text @d1 2 a2 2 # $NetBSD: Theory,v 1.2 1998/01/09 04:11:55 perry Exp $ @@(#)Theory 7.6 d10 1 d288 169 @ 1.3.6.1 log @Pull up to last week's -current. @ text @d1 2 a2 2 # $NetBSD: Theory,v 1.4 1999/11/10 20:32:31 kleink Exp $ @@(#)Theory 7.9 a9 1 Calendrical issues a286 169 ----- Calendrical issues ----- Calendrical issues are a bit out of scope for a time zone database, but they indicate the sort of problems that we would run into if we extended the time zone database further into the past. An excellent resource in this area is Nachum Dershowitz and Edward M. Reingold, Calendrical Calculations , Cambridge University Press (1997). Other information and sources are given below. They sometimes disagree. France Gregorian calendar adopted 1582-12-20. French Revolutionary calendar used 1793-11-24 through 1805-12-31, and (in Paris only) 1871-05-06 through 1871-05-23. Russia From Chris Carrier <72157.3334@@CompuServe.COM> (1996-12-02): On 1929-10-01 the Soviet Union instituted an ``Eternal Calendar'' with 30-day months plus 5 holidays, with a 5-day week. On 1931-12-01 it changed to a 6-day week; in 1934 it reverted to the Gregorian calendar while retaining the 6-day week; on 1940-06-27 it reverted to the 7-day week. With the 6-day week the usual days off were the 6th, 12th, 18th, 24th and 30th of the month. (Source: Evitiar Zerubavel, _The Seven Day Circle_) Mark Brader reported a similar story in "The Book of Calendars", edited by Frank Parise (1982, Facts on File, ISBN 0-8719-6467-8), page 377. But: From: Petteri Sulonen (via Usenet) Date: 14 Jan 1999 00:00:00 GMT Message-ID: If your source is correct, how come documents between 1929 -- 1940 were still dated using the conventional, Gregorian calendar? I can post a scan of a document dated December 1, 1934, signed by Yenukidze, the secretary, on behalf of Kalinin, the President of the Executive Committee of the Supreme Soviet, if you like. Sweden (and Finland) From: msb@@sq.com (Mark Brader) Subject: Re: Gregorian reform -- a part of locale? Date: 1996-07-06 In 1700, Denmark made the transition from Julian to Gregorian. Sweden decided to *start* a transition in 1700 as well, but rather than have one of those unsightly calendar gaps :-), they simply decreed that the next leap year after 1696 would be in 1744 -- putting the whole country on a calendar different from both Julian and Gregorian for a period of 40 years. However, in 1704 something went wrong and the plan was not carried through; they did, after all, have a leap year that year. And one in 1708. In 1712 they gave it up and went back to Julian, putting 30 days in February that year!... Then in 1753, Sweden made the transition to Gregorian in the usual manner, getting there only 13 years behind the original schedule. (A previous posting of this story was challenged, and Swedish readers produced the following references to support it: "Tiderakning och historia" by Natanael Beckman (1924) and "Tid, en bok om tiderakning och kalendervasen" by Lars-Olof Lode'n (no date was given).) Grotefend's data From: "Michael Palmer" [with one obvious typo fixed] Subject: Re: Gregorian Calendar (was Re: Another FHC related question Newsgroups: soc.genealogy.german Date: Tue, 9 Feb 1999 02:32:48 -800 Message-ID: <199902091032.CAA09644@@netcom10.netcom.com> The following is a(n incomplete) listing, arranged chronologically, of European states, with the date they converted from the Julian to the Gregorian calendar: 04/15 Oct 1582 - Italy (with exceptions), Spain, Portugal, Poland (Roman Catholics and Danzig only) 09/20 Dec 1582 - France, Lorraine 21 Dec 1582/ 01 Jan 1583 - Holland, Brabant, Flanders, Hennegau 10/21 Feb 1583 - bishopric of Liege (L"uttich) 13/24 Feb 1583 - bishopric of Augsburg 04/15 Oct 1583 - electorate of Trier 05/16 Oct 1583 - Bavaria, bishoprics of Freising, Eichstedt, Regensburg, Salzburg, Brixen 13/24 Oct 1583 - Austrian Oberelsass and Breisgau 20/31 Oct 1583 - bishopric of Basel 02/13 Nov 1583 - duchy of J"ulich-Berg 02/13 Nov 1583 - electorate and city of K"oln 04/15 Nov 1583 - bishopric of W"urzburg 11/22 Nov 1583 - electorate of Mainz 16/27 Nov 1583 - bishopric of Strassburg and the margraviate of Baden 17/28 Nov 1583 - bishopric of M"unster and duchy of Cleve 14/25 Dec 1583 - Steiermark 06/17 Jan 1584 - Austria and Bohemia 11/22 Jan 1584 - Luzern, Uri, Schwyz, Zug, Freiburg, Solothurn 12/23 Jan 1584 - Silesia and the Lausitz 22 Jan/ 02 Feb 1584 - Hungary (legally on 21 Oct 1587) Jun 1584 - Unterwalden 01/12 Jul 1584 - duchy of Westfalen 16/27 Jun 1585 - bishopric of Paderborn 14/25 Dec 1590 - Transylvania 22 Aug/ 02 Sep 1612 - duchy of Prussia 13/24 Dec 1614 - Pfalz-Neuburg 1617 - duchy of Kurland (reverted to the Julian calendar in 1796) 1624 - bishopric of Osnabr"uck 1630 - bishopric of Minden 15/26 Mar 1631 - bishopric of Hildesheim 1655 - Kanton Wallis 05/16 Feb 1682 - city of Strassburg 18 Feb/ 01 Mar 1700 - Protestant Germany (including Swedish possessions in Germany), Denmark, Norway 30 Jun/ 12 Jul 1700 - Gelderland, Zutphen 10 Nov/ 12 Dec 1700 - Utrecht, Overijssel 31 Dec 1700/ 12 Jan 1701 - Friesland, Groningen, Z"urich, Bern, Basel, Geneva, Turgau, and Schaffhausen 1724 - Glarus, Appenzell, and the city of St. Gallen 01 Jan 1750 - Pisa and Florence 02/14 Sep 1752 - Great Britain 17 Feb/ 01 Mar 1753 - Sweden 1760-1812 - Graub"unden The Russian empire (including Finland and the Baltic states) did not convert to the Gregorian calendar until the Soviet revolution of 1917. Source: H. Grotefend, _Taschenbuch der Zeitrechnung des deutschen Mittelalters und der Neuzeit_, herausgegeben von Dr. O. Grotefend (Hannover: Hahnsche Buchhandlung, 1941), pp. 26-28. @ 1.2 log @RCS Id Police. @ text @d1 2 a2 2 # $NetBSD$ from: @@(#)Theory 7.5 d75 1 a75 1 variable. While an administrator can "do everything in GMT" to get d161 1 a161 1 time_t values when doing conversions for places that don't use GMT. d285 1 a285 1 to use numeric GMT offsets like `-0500' instead of time zone @ 1.1 log @Initial revision @ text @d1 2 a2 1 @@(#)Theory 7.2 d4 27 a30 12 These time and date functions are much like the System V Release 2.0 (SVR2) time and date functions; there are a few additions and changes to extend the usefulness of the SVR2 functions: * In SVR2, time display in a process is controlled by the environment variable TZ, which "must be a three-letter time zone name, followed by a number representing the difference between local time and Greenwich Mean Time in hours, followed by an optional three-letter name for a daylight time zone;" when the optional daylight time zone is present, "standard U.S.A. Daylight Savings Time conversion is applied." This means that SVR2 can't deal with other (for example, Australian) daylight savings time rules, or situations where more than two d33 35 a67 2 * In SVR2, time conversion information is compiled into each program that does time conversion. This means that when time conversion d71 1 a71 4 * In SVR2, time conversion fails for near-minimum or near-maximum time_t values when doing conversions for places that don't use GMT. * In SVR2, there's no tamper-proof way for a process to learn the d77 1 a77 1 daylight savings time shifts--as might be required to limit phone d80 1 a80 2 * These functions can account for leap seconds, thanks to Bradley White (bww@@k.cs.cmu.edu). d82 1 a82 1 These are the changes that have been made to the SVR2 functions: d95 1 a95 1 take on values such as "US/Eastern" might cause "old" programs d110 1 a110 1 abbreviation to be used. This differs from SVR2, where the elements d115 1 a115 2 needed or supported. (You can use a compile-time option to cause these variables to be defined and to be set by "tzset"; however, their d126 2 a127 2 "tzsetwall();" if such code is moved to "old" systems that don't provide tzsetwall, you won't be able to generate an executable program. d133 2 a134 1 Points of interest to folks with Version 7 or BSD systems: d136 12 a147 1 * The BSD "timezone" function is not present in this package; d153 6 a158 2 zone abbreviation to use. Alternatively, use localtime(&clock)->tm_zone if this has been enabled. d160 8 a167 11 * The BSD gettimeofday function is not used in this package; this lets users control the time zone used in doing time conversions. Users who don't try to control things (that is, users who do not set the environment variable TZ) get the time conversion specified in the file "/etc/zoneinfo/localtime"; see the time zone compiler writeup for information on how to initialize this file. The functions that are conditionally compiled if STD_INSPIRED is defined should, at this point, be looked on primarily as food for thought. They are not in any sense "standard compatible"--some are not, in fact, specified in *any* standard. They do, however, represent responses of various authors to d175 1 a175 1 close to SVR2 (with the exceptions outlined above) to ensure its broad d178 109 @ 1.1.1.1 log @Strictly speaking, these files probably don't belong in the libc sources. On the other hand, it makes it easier to track the master tzcode sources if we try to keep the distribution together as much as possible. The zic and zdump commands will access the files the need with make's .PATH facility. @ text @@ 1.1.1.1.2.1 log @file Theory was added on branch ivory_soap on 1995-03-10 07:08:17 +0000 @ text @d1 120 @ 1.1.1.1.2.2 log @Strictly speaking, these files probably don't belong in the libc sources. On the other hand, it makes it easier to track the master tzcode sources if we try to keep the distribution together as much as possible. The zic and zdump commands will access the files the need with make's .PATH facility. @ text @a0 120 @@(#)Theory 7.2 These time and date functions are much like the System V Release 2.0 (SVR2) time and date functions; there are a few additions and changes to extend the usefulness of the SVR2 functions: * In SVR2, time display in a process is controlled by the environment variable TZ, which "must be a three-letter time zone name, followed by a number representing the difference between local time and Greenwich Mean Time in hours, followed by an optional three-letter name for a daylight time zone;" when the optional daylight time zone is present, "standard U.S.A. Daylight Savings Time conversion is applied." This means that SVR2 can't deal with other (for example, Australian) daylight savings time rules, or situations where more than two time zone abbreviations are used in an area. * In SVR2, time conversion information is compiled into each program that does time conversion. This means that when time conversion rules change (as in the United States in 1987), all programs that do time conversion must be recompiled to ensure proper results. * In SVR2, time conversion fails for near-minimum or near-maximum time_t values when doing conversions for places that don't use GMT. * In SVR2, there's no tamper-proof way for a process to learn the system's best idea of local wall clock. (This is important for applications that an administrator wants used only at certain times-- without regard to whether the user has fiddled the "TZ" environment variable. While an administrator can "do everything in GMT" to get around the problem, doing so is inconvenient and precludes handling daylight savings time shifts--as might be required to limit phone calls to off-peak hours.) * These functions can account for leap seconds, thanks to Bradley White (bww@@k.cs.cmu.edu). These are the changes that have been made to the SVR2 functions: * The "TZ" environment variable is used in generating the name of a file from which time zone information is read (or is interpreted a la POSIX); "TZ" is no longer constrained to be a three-letter time zone name followed by a number of hours and an optional three-letter daylight time zone name. The daylight saving time rules to be used for a particular time zone are encoded in the time zone file; the format of the file allows U.S., Australian, and other rules to be encoded, and allows for situations where more than two time zone abbreviations are used. It was recognized that allowing the "TZ" environment variable to take on values such as "US/Eastern" might cause "old" programs (that expect "TZ" to have a certain form) to operate incorrectly; consideration was given to using some other environment variable (for example, "TIMEZONE") to hold the string used to generate the time zone information file name. In the end, however, it was decided to continue using "TZ": it is widely used for time zone purposes; separately maintaining both "TZ" and "TIMEZONE" seemed a nuisance; and systems where "new" forms of "TZ" might cause problems can simply use TZ values such as "EST5EDT" which can be used both by "new" programs (a la POSIX) and "old" programs (as zone names and offsets). * To handle places where more than two time zone abbreviations are used, the functions "localtime" and "gmtime" set tzname[tmp->tm_isdst] (where "tmp" is the value the function returns) to the time zone abbreviation to be used. This differs from SVR2, where the elements of tzname are only changed as a result of calls to tzset. * Since the "TZ" environment variable can now be used to control time conversion, the "daylight" and "timezone" variables are no longer needed or supported. (You can use a compile-time option to cause these variables to be defined and to be set by "tzset"; however, their values will not be used by "localtime.") * The "localtime" function has been set up to deliver correct results for near-minimum or near-maximum time_t values. (A comment in the source code tells how to get compatibly wrong results). * A function "tzsetwall" has been added to arrange for the system's best approximation to local wall clock time to be delivered by subsequent calls to "localtime." Source code for portable applications that "must" run on local wall clock time should call "tzsetwall();" if such code is moved to "old" systems that don't provide tzsetwall, you won't be able to generate an executable program. (These time zone functions also arrange for local wall clock time to be used if tzset is called--directly or indirectly--and there's no "TZ" environment variable; portable applications should not, however, rely on this behavior since it's not the way SVR2 systems behave.) Points of interest to folks with Version 7 or BSD systems: * The BSD "timezone" function is not present in this package; it's impossible to reliably map timezone's arguments (a "minutes west of GMT" value and a "daylight saving time in effect" flag) to a time zone abbreviation, and we refuse to guess. Programs that in the past used the timezone function may now examine tzname[localtime(&clock)->tm_isdst] to learn the correct time zone abbreviation to use. Alternatively, use localtime(&clock)->tm_zone if this has been enabled. * The BSD gettimeofday function is not used in this package; this lets users control the time zone used in doing time conversions. Users who don't try to control things (that is, users who do not set the environment variable TZ) get the time conversion specified in the file "/etc/zoneinfo/localtime"; see the time zone compiler writeup for information on how to initialize this file. The functions that are conditionally compiled if STD_INSPIRED is defined should, at this point, be looked on primarily as food for thought. They are not in any sense "standard compatible"--some are not, in fact, specified in *any* standard. They do, however, represent responses of various authors to standardization proposals. Other time conversion proposals, in particular the one developed by folks at Hewlett Packard, offer a wider selection of functions that provide capabilities beyond those provided here. The absence of such functions from this package is not meant to discourage the development, standardization, or use of such functions. Rather, their absence reflects the decision to make this package close to SVR2 (with the exceptions outlined above) to ensure its broad acceptability. If more powerful time conversion functions can be standardized, so much the better. @ 1.1.1.2 log @import tzcode96a @ text @d1 1 a1 1 @@(#)Theory 7.4 d50 1 a50 1 take on values such as "America/New_York" might cause "old" programs d82 2 a83 2 "tzsetwall();" if such code is moved to "old" systems that don't provide tzsetwall, you won't be able to generate an executable program. d97 2 a98 2 zone abbreviation to use. Alternatively, use localtime(&clock)->tm_zone if this has been enabled. d107 4 a110 4 The functions that are conditionally compiled if STD_INSPIRED is defined should, at this point, be looked on primarily as food for thought. They are not in any sense "standard compatible"--some are not, in fact, specified in *any* standard. They do, however, represent responses of various authors to @ 1.1.1.3 log @import tzcode1997g @ text @d1 1 a1 1 @@(#)Theory 7.5 d3 12 a14 27 ----- Outline ----- Time and date functions Names of time zone regions Time zone abbreviations ----- Time and date functions ----- These time and date functions are upwards compatible with POSIX.1, an international standard for Unix-like systems. As of this writing, the current edition of POSIX.1 is: Information technology --Portable Operating System Interface (POSIX (R)) -- Part 1: System Application Program Interface (API) [C Language] ISO/IEC 9945-1:1996 ANSI/IEEE Std 1003.1, 1996 Edition 1996-07-12 POSIX.1 has the following properties and limitations. * In POSIX.1, time display in a process is controlled by the environment variable TZ. Unfortunately, the POSIX.1 TZ string takes a form that is hard to describe and is error-prone in practice. Also, POSIX.1 TZ strings can't deal with other (for example, Israeli) daylight saving time rules, or situations where more than two d17 2 a18 35 The POSIX.1 TZ string takes the following form: stdoffset[dst[offset],date[/time],date[/time]] where: std and dst are 3 or more characters specifying the standard and daylight saving time (DST) zone names. offset is of the form `[-]hh:[mm[:ss]]' and specifies the offset west of UTC. The default DST offset is one hour ahead of standard time. date[/time],date[/time] specifies the beginning and end of DST. If this is absent, the system supplies its own rules for DST, and these can differ from year to year; typically US DST rules are used. time takes the form `hh:[mm[:ss]]' and defaults to 02:00. date takes one of the following forms: Jn (1<=n<=365) origin-1 day number not counting February 29 n (0<=n<=365) origin-0 day number counting February 29 if present Mm.n.d (0[Sunday]<=d<=6[Saturday], 1<=n<=5, 1<=m<=12) for the dth day of week n of month m of the year, where week 1 is the first week in which day d appears, and `5' stands for the last week in which day d appears (which may be either the 4th or 5th week). * In POSIX.1, when a TZ value like "EST5EDT" is parsed, typically the current US DST rules are used, but this means that the US DST rules are compiled into each program that does time conversion. This means that when US time conversion d22 4 a25 1 * In POSIX.1, there's no tamper-proof way for a process to learn the d31 1 a31 1 daylight saving time shifts--as might be required to limit phone d34 2 a35 1 * POSIX.1 requires that systems ignore leap seconds. d37 1 a37 1 These are the extensions that have been made to the POSIX.1 functions: d65 1 a65 1 abbreviation to be used. This differs from POSIX.1, where the elements d70 2 a71 1 needed. (These variables are defined and set by "tzset"; however, their d89 1 a89 13 * These functions can account for leap seconds, thanks to Bradley White (bww@@k.cs.cmu.edu). Points of interest to folks with other systems: * This package is already part of many POSIX-compliant hosts, including BSD, HP, Linux, Network Appliance, SCO, SGI, and Sun. On such hosts, the primary use of this package is to update obsolete time zone rule tables. To do this, you may need to compile the time zone compiler `zic' supplied with this package instead of using the system `zic', since the format of zic's input changed slightly in late 1994, and many vendors still do not support the new input format. d91 1 a91 1 * The Unix Version 7 "timezone" function is not present in this package; d100 6 a105 7 * The 4.2BSD gettimeofday function is not used in this package. This formerly let users obtain the current UTC offset and DST flag, but this functionality was removed in later versions of BSD. * In SVR2, time conversion fails for near-minimum or near-maximum time_t values when doing conversions for places that don't use GMT. This package takes care to do these conversions correctly. d118 1 a118 1 contain valid extensions to POSIX.1, to ensure its broad a120 109 ----- Names of time zone rule files ----- The names of this package's installed time zone rule files are chosen to help minimize possible future incompatibilities due to political events. Ordinarily, names of countries are not used, to avoid incompatibilities when countries change their name (e.g. Zaire->Congo) or when locations change countries (e.g. Hong Kong from UK colony to China). Names normally have the form AREA/LOCATION, where AREA is the name of a continent or ocean, and LOCATION is the name of a specific location within that region. North and South America share the same area, `America'. Typical names are `Africa/Cairo', `America/New_York', and `Pacific/Honolulu'. Here are the general rules used for choosing location names, in decreasing order of importance: Use only valid Posix file names. Use only Ascii letters, digits, `.', `-' and `_'. Do not exceed 14 characters or start with `-'. E.g. prefer `Brunei' to `Bandar_Seri_Begawan'. Include at least one location per time zone rule set per country. One such location is enough. If all the clocks in a country's region have agreed since 1970, don't bother to include more than one location even if subregions' clocks disagreed before 1970. Otherwise these tables would become annoyingly large. If a name is ambiguous, use a less ambiguous alternative; e.g. many cities are named San Jose and Georgetown, so prefer `Costa_Rica' to `San_Jose' and `Guyana' to `Georgetown'. Keep locations compact. Use cities or small islands, not countries or regions, so that any future time zone changes do not split locations into different time zones. E.g. prefer `Paris' to `France', since France has had multiple time zones. Use traditional English spelling, e.g. prefer `Rome' to `Roma', and prefer `Athens' to the true name (which uses Greek letters). The Posix file name restrictions encourage this rule. Use the most populous among locations in a country's time zone, e.g. prefer `Shanghai' to `Beijing'. Among locations with similar populations, pick the best-known location, e.g. prefer `Rome' to `Milan'. Use the singular form, e.g. prefer `Canary' to `Canaries'. Omit common suffixes like `_Islands' and `_City', unless that would lead to ambiguity. E.g. prefer `Cayman' to `Cayman_Islands' and `Guatemala' to `Guatemala_City', but prefer `Mexico_City' to `Mexico' because the country of Mexico has several time zones. Use `_' to represent a space. Omit `.' from abbreviations in names, e.g. prefer `St_Helena' to `St._Helena'. The file `zone.tab' lists the geographical locations used to name time zone rule files. Older versions of this package used a different naming scheme, and these older names are still supported. See the file `backwards' for most of these older names (e.g. `US/Eastern' instead of `America/New_York'). The other old-fashioned names still supported are `WET', `CET', `MET', `EET' (see the file `europe'), and `Factory' (see the file `factory'). ----- Time zone abbreviations ----- When this package is installed, it generates time zone abbreviations like `EST' to be compatible with human tradition and POSIX.1. Here are the general rules used for choosing time zone abbreviations, in decreasing order of importance: Use abbreviations that consist of 3 or more upper-case Ascii letters, except use "___" for locations while uninhabited. Posix.1 requires at least 3 characters, and the restriction to upper-case Ascii letters follows most traditions. Previous editions of this database also used characters like ' ' and '?', but these characters have a special meaning to the shell and cause commands like set `date` to have unexpected effects. In theory, the character set could be !%./@@A-Z^_a-z{}, but these tables use only upper-case Ascii letters (and "___"). Use abbreviations that are in common use among English-speakers, e.g. `EST' for Eastern Standard Time in North America. We assume that applications translate them to other languages as part of the normal localization process; for example, a French application might translate `EST' to `HNE'. For zones whose times are taken from a city's longitude, use the traditional xMT notation, e.g. `PMT' for Paris Mean Time. The only name like this in current use is `GMT'. If there is no common English abbreviation, abbreviate the English translation of the usual phrase used by native speakers. If this is not available or is a phrase mentioning the country (e.g. ``Cape Verde Time''), then: When a country has a single or principal time zone region, append `T' to the country's ISO code, e.g. `CVT' for Cape Verde Time. For summer time append `ST'; for double summer time append `DST'; etc. When a country has multiple time zones, take the first three letters of an English place name identifying each zone and then append `T', `ST', etc. as before; e.g. `VLAST' for VLAdivostok Summer Time. Application writers should note that these abbreviations are ambiguous in practice: e.g. `EST' has a different meaning in Australia than it does in the United States. In new applications, it's often better to use numeric GMT offsets like `-0500' instead of time zone abbreviations like `EST'; this avoids the ambiguity. @ 1.1.1.4 log @import tzcode1998a @ text @d1 1 a1 1 @@(#)Theory 7.6 d74 1 a74 1 variable. While an administrator can "do everything in UTC" to get d160 1 a160 1 time_t values when doing conversions for places that don't use UTC. d284 1 a284 1 to use numeric UTC offsets like `-0500' instead of time zone @ 1.1.1.5 log @Import tzcode1999h. @ text @d1 1 a1 1 @@(#)Theory 7.9 a8 1 Calendrical issues a285 169 ----- Calendrical issues ----- Calendrical issues are a bit out of scope for a time zone database, but they indicate the sort of problems that we would run into if we extended the time zone database further into the past. An excellent resource in this area is Nachum Dershowitz and Edward M. Reingold, Calendrical Calculations , Cambridge University Press (1997). Other information and sources are given below. They sometimes disagree. France Gregorian calendar adopted 1582-12-20. French Revolutionary calendar used 1793-11-24 through 1805-12-31, and (in Paris only) 1871-05-06 through 1871-05-23. Russia From Chris Carrier <72157.3334@@CompuServe.COM> (1996-12-02): On 1929-10-01 the Soviet Union instituted an ``Eternal Calendar'' with 30-day months plus 5 holidays, with a 5-day week. On 1931-12-01 it changed to a 6-day week; in 1934 it reverted to the Gregorian calendar while retaining the 6-day week; on 1940-06-27 it reverted to the 7-day week. With the 6-day week the usual days off were the 6th, 12th, 18th, 24th and 30th of the month. (Source: Evitiar Zerubavel, _The Seven Day Circle_) Mark Brader reported a similar story in "The Book of Calendars", edited by Frank Parise (1982, Facts on File, ISBN 0-8719-6467-8), page 377. But: From: Petteri Sulonen (via Usenet) Date: 14 Jan 1999 00:00:00 GMT Message-ID: If your source is correct, how come documents between 1929 -- 1940 were still dated using the conventional, Gregorian calendar? I can post a scan of a document dated December 1, 1934, signed by Yenukidze, the secretary, on behalf of Kalinin, the President of the Executive Committee of the Supreme Soviet, if you like. Sweden (and Finland) From: msb@@sq.com (Mark Brader) Subject: Re: Gregorian reform -- a part of locale? Date: 1996-07-06 In 1700, Denmark made the transition from Julian to Gregorian. Sweden decided to *start* a transition in 1700 as well, but rather than have one of those unsightly calendar gaps :-), they simply decreed that the next leap year after 1696 would be in 1744 -- putting the whole country on a calendar different from both Julian and Gregorian for a period of 40 years. However, in 1704 something went wrong and the plan was not carried through; they did, after all, have a leap year that year. And one in 1708. In 1712 they gave it up and went back to Julian, putting 30 days in February that year!... Then in 1753, Sweden made the transition to Gregorian in the usual manner, getting there only 13 years behind the original schedule. (A previous posting of this story was challenged, and Swedish readers produced the following references to support it: "Tiderakning och historia" by Natanael Beckman (1924) and "Tid, en bok om tiderakning och kalendervasen" by Lars-Olof Lode'n (no date was given).) Grotefend's data From: "Michael Palmer" [with one obvious typo fixed] Subject: Re: Gregorian Calendar (was Re: Another FHC related question Newsgroups: soc.genealogy.german Date: Tue, 9 Feb 1999 02:32:48 -800 Message-ID: <199902091032.CAA09644@@netcom10.netcom.com> The following is a(n incomplete) listing, arranged chronologically, of European states, with the date they converted from the Julian to the Gregorian calendar: 04/15 Oct 1582 - Italy (with exceptions), Spain, Portugal, Poland (Roman Catholics and Danzig only) 09/20 Dec 1582 - France, Lorraine 21 Dec 1582/ 01 Jan 1583 - Holland, Brabant, Flanders, Hennegau 10/21 Feb 1583 - bishopric of Liege (L"uttich) 13/24 Feb 1583 - bishopric of Augsburg 04/15 Oct 1583 - electorate of Trier 05/16 Oct 1583 - Bavaria, bishoprics of Freising, Eichstedt, Regensburg, Salzburg, Brixen 13/24 Oct 1583 - Austrian Oberelsass and Breisgau 20/31 Oct 1583 - bishopric of Basel 02/13 Nov 1583 - duchy of J"ulich-Berg 02/13 Nov 1583 - electorate and city of K"oln 04/15 Nov 1583 - bishopric of W"urzburg 11/22 Nov 1583 - electorate of Mainz 16/27 Nov 1583 - bishopric of Strassburg and the margraviate of Baden 17/28 Nov 1583 - bishopric of M"unster and duchy of Cleve 14/25 Dec 1583 - Steiermark 06/17 Jan 1584 - Austria and Bohemia 11/22 Jan 1584 - Luzern, Uri, Schwyz, Zug, Freiburg, Solothurn 12/23 Jan 1584 - Silesia and the Lausitz 22 Jan/ 02 Feb 1584 - Hungary (legally on 21 Oct 1587) Jun 1584 - Unterwalden 01/12 Jul 1584 - duchy of Westfalen 16/27 Jun 1585 - bishopric of Paderborn 14/25 Dec 1590 - Transylvania 22 Aug/ 02 Sep 1612 - duchy of Prussia 13/24 Dec 1614 - Pfalz-Neuburg 1617 - duchy of Kurland (reverted to the Julian calendar in 1796) 1624 - bishopric of Osnabr"uck 1630 - bishopric of Minden 15/26 Mar 1631 - bishopric of Hildesheim 1655 - Kanton Wallis 05/16 Feb 1682 - city of Strassburg 18 Feb/ 01 Mar 1700 - Protestant Germany (including Swedish possessions in Germany), Denmark, Norway 30 Jun/ 12 Jul 1700 - Gelderland, Zutphen 10 Nov/ 12 Dec 1700 - Utrecht, Overijssel 31 Dec 1700/ 12 Jan 1701 - Friesland, Groningen, Z"urich, Bern, Basel, Geneva, Turgau, and Schaffhausen 1724 - Glarus, Appenzell, and the city of St. Gallen 01 Jan 1750 - Pisa and Florence 02/14 Sep 1752 - Great Britain 17 Feb/ 01 Mar 1753 - Sweden 1760-1812 - Graub"unden The Russian empire (including Finland and the Baltic states) did not convert to the Gregorian calendar until the Soviet revolution of 1917. Source: H. Grotefend, _Taschenbuch der Zeitrechnung des deutschen Mittelalters und der Neuzeit_, herausgegeben von Dr. O. Grotefend (Hannover: Hahnsche Buchhandlung, 1941), pp. 26-28. @ 1.1.1.6 log @Import tzcode2000g. @ text @d1 1 a1 1 @@(#)Theory 7.11 d201 1 a201 2 One such location is enough. Use ISO 3166 (see the file iso3166.tab) to help decide whether something is a country. a228 6 Do not change established names if they only marginally violate the above rules. For example, don't change the existing name `Rome' to `Milan' merely because Milan's population has grown to be somewhat greater than Rome's. If a name is changed, put its old spelling in the `backward' file. d235 1 a235 1 See the file `backward' for most of these older names @ 1.1.1.7 log @Import tzcode2002b. @ text @d1 1 a1 1 @@(#)Theory 7.13 d38 1 a38 1 d182 5 a186 28 The time zone rule file naming conventions attempt to strike a balance among the following goals: * Uniquely identify every national region where clocks have all agreed since 1970. This is essential for the intended use: static clocks keeping local civil time. * Indicate to humans as to where that region is. This simplifes use. * Be robust in the presence of political changes. This reduces the number of updates and backward-compatibility hacks. For example, names of countries are ordinarily not used, to avoid incompatibilities when countries change their name (e.g. Zaire->Congo) or when locations change countries (e.g. Hong Kong from UK colony to China). * Be portable to a wide variety of implementations. This promotes use of the technology. * Use a consistent naming convention over the entire world. This simplifies both use and maintenance. This naming convention is not intended for use by inexperienced users to select TZ values by themselves (though they can of course examine and reuse existing settings). Distributors should provide documentation and/or a simple selection interface that explains the names; see the 'tzselect' program supplied with this distribution for one example. d197 3 a199 7 Use only valid POSIX file name components (i.e., the parts of names other than `/'). Within a file name component, use only ASCII letters, `.', `-' and `_'. Do not use digits, as that might create an ambiguity with POSIX TZ strings. A file name component must not exceed 14 characters or start with `-'. E.g., prefer `Brunei' to `Bandar_Seri_Begawan'. d214 1 a214 1 Use mainstream English spelling, e.g. prefer `Rome' to `Roma', and d216 1 a216 1 The POSIX file name restrictions encourage this rule. d256 4 a259 1 Use abbreviations that consist of three or more ASCII letters. d264 3 a266 18 to have unexpected effects. Previous editions of this rule required upper-case letters, but the Congressman who introduced Chamorro Standard Time preferred "ChST", so the rule has been relaxed. This rule guarantees that all abbreviations could have been specified by a POSIX.1 TZ string. POSIX.1 requires at least three characters for an abbreviation. POSIX.1-1996 says that an abbreviation cannot start with ':', and cannot contain ',', '-', '+', NUL, or a digit. Draft 7 of POSIX 1003.1-200x changes this rule to say that an abbreviation can contain only '-', '+', and alphanumeric characters in the current locale. To be portable to both sets of rules, an abbreviation must therefore use only ASCII letters, as these are the only letters that are alphabetic in all locales. a271 1 a274 1 a288 3 Use "zzz" for locations while uninhabited. The mnemonic is that these locations are, in some sense, asleep. d379 2 a380 2 The following is a(n incomplete) listing, arranged chronologically, of European states, with the date they converted from the Julian to the d457 1 a457 1 The Russian empire (including Finland and the Baltic states) did not d460 2 a461 2 Source: H. Grotefend, _Taschenbuch der Zeitrechnung des deutschen Mittelalters und der Neuzeit_, herausgegeben von Dr. O. Grotefend @ 1.1.1.8 log @Import tzcode2003e. @ text @d1 1 a1 1 @@(#)Theory 7.14 d15 1 a15 1 an international standard for UNIX-like systems. d147 1 a147 1 * The UNIX Version 7 "timezone" function is not present in this package; @ 1.1.1.9 log @Import tzcode2004a. @ text @d1 1 a1 1 @@(#)Theory 7.15 a9 1 Time and time zones on Mars a506 45 ----- Time and time zones on Mars ----- Some people have adjusted their work schedules to fit Mars time. Dozens of special Mars watches were built for Jet Propulsion Laboratory workers who kept Mars time during the Mars Exploration Rovers mission (2004). These timepieces look like normal Seikos and Citizens but use Mars seconds rather than terrestrial seconds. A Mars solar day is called a "sol" and has a mean period equal to about 24 hours 39 minutes 35.244 seconds in terrestrial time. It is divided into a conventional 24-hour clock, so each Mars second equals about 1.02749125 terrestrial seconds. The prime meridian of Mars goes through the center of the crater Airy-0, named in honor of the British astronomer who built the Greenwich telescope that defines Earth's prime meridian. Mean solar time on the Mars prime meridian is called Mars Coordinated Time (MTC). Each landed mission on Mars has adopted a different reference for solar time keeping, so there is no real standard for Mars time zones. For example, the Mars Exploration Rover project (2004) defined two time zones "Local Solar Time A" and "Local Solar Time B" for its two missions, each zone designed so that its time equals local true solar time at approximately the middle of the nominal mission. Such a "time zone" is not particularly suited for any application other than the mission itself. Many calendars have been proposed for Mars, but none have achieved wide acceptance. Astronomers often use Mars Sol Date (MSD) which is a sequential count of Mars solar days elapsed since about 1873-12-29 12:00 GMT. The tz database does not currently support Mars time, but it is documented here in the hopes that support will be added eventually. Sources: Michael Allison and Robert Schmunk, "Technical Notes on Mars Solar Time as Adopted by the Mars24 Sunclock" (2004-03-15). Jia-Rui Chong, "Workdays Fit for a Martian", Los Angeles Times (2004-01-14), pp A1, A20-A21. @ 1.1.1.10 log @import tzcode2009k @ text @d1 2 a2 3 @@(#)Theory 8.3 This file is in the public domain, so clarified as of 2009-05-17 by Arthur David Olson. d12 1 d15 1 a15 1 These time and date functions are upwards compatible with POSIX, d17 1 a17 1 As of this writing, the current edition of POSIX is: d19 5 a23 6 Standard for Information technology -- Portable Operating System Interface (POSIX (R)) -- System Interfaces IEEE Std 1003.1, 2004 Edition d25 1 a25 1 POSIX has the following properties and limitations. d27 2 a28 2 * In POSIX, time display in a process is controlled by the environment variable TZ. Unfortunately, the POSIX TZ string takes d30 1 a30 1 Also, POSIX TZ strings can't deal with other (for example, Israeli) d34 1 a34 1 The POSIX TZ string takes the following form: a42 3 Starting with POSIX.1-2001, std and dst may also be in a quoted form like ""; this allows "+" and "-" in the names. d65 2 a66 13 Here is an example POSIX TZ string, for US Pacific time using rules appropriate from 1987 through 2006: TZ='PST8PDT,M4.1.0/02:00,M10.5.0/02:00' This POSIX TZ string is hard to remember, and mishandles time stamps before 1987 and after 2006. With this package you can use this instead: TZ='America/Los_Angeles' * POSIX does not define the exact meaning of TZ values like "EST5EDT". Typically the current US DST rules are used to interpret such values, d72 1 a72 1 * In POSIX, there's no tamper-proof way for a process to learn the d81 1 a81 1 * POSIX requires that systems ignore leap seconds. d83 1 a83 1 These are the extensions that have been made to the POSIX functions: d111 1 a111 1 abbreviation to be used. This differs from POSIX, where the elements d134 2 a135 1 * These functions can account for leap seconds, thanks to Bradley White. d176 3 a178 3 contain valid extensions to POSIX, to ensure its broad acceptability. If more powerful time conversion functions can be standardized, so much the better. a230 2 However, uninhabited ISO 3166 regions like Bouvet Island do not need locations, since local time is not defined there. d266 1 a266 2 time zone rule files. It is intended to be an exhaustive list of canonical names for geographic regions. d280 1 a280 1 like `EST' to be compatible with human tradition and POSIX. d295 1 a295 1 been specified by a POSIX TZ string. POSIX d297 1 a297 1 abbreviation. POSIX through 2000 says that an abbreviation d299 4 a302 4 '+', NUL, or a digit. POSIX from 2001 on changes this rule to say that an abbreviation can contain only '-', '+', and alphanumeric characters from the portable character set in the current locale. To be portable to both sets of d304 2 a305 1 letters. d331 2 a332 3 Use UTC (with time zone abbreviation "zzz") for locations while uninhabited. The "zzz" mnemonic is that these locations are, in some sense, asleep. d346 4 a349 4 resource in this area is Edward M. Reingold and Nachum Dershowitz, Calendrical Calculations: The Millennium Edition , Cambridge University Press (2001). Other information and d362 1 a362 1 From Chris Carrier (1996-12-02): d377 1 a377 1 ... d390 1 a390 1 From: Mark Brader d418 1 a418 1 From: "Michael Palmer" [with one obvious typo fixed] d422 1 a422 1 ... d549 1 a549 1 (2004-07-30). @