ZDUMP(8) | System Manager's Manual | ZDUMP(8) |
zdump
— timezone
dumper
zdump |
[--version ] [-v ]
[-V ] [-c
[loyear,]highyear] [timezone
...] |
zdump |
-t [lotime,]hightime
[zonename ...] |
The zdump
program prints the current time
in each timezone named on the command line. A
timezone
of “-” is treated as if it
were /dev/stdin; this can be used to pipe TZif data
into zdump
.
--version
--help
-i
-v
-c
[loyear,]highyear-t
[lotime,]hightime-c
, the cutoff's lower bound is
inclusive and its upper bound is exclusive.-V
-v
, except omit output concerning extreme
time and year values. This generates output that is easier to compare to
that of implementations with different time representations.The interval format is a compact text representation that is
intended to be both human- and machine-readable. It consists of an empty
line, then a line “TZ=string” where
string
is a double-quoted string giving the
timezone, a second line “- - interval” describing the time
interval before the first transition if any, and zero or more following
lines “date time interval” one line for each transition time
and following interval. Fields are separated by single tabs.
Dates are in yyyy-mm-dd
format and times
are in 24-hour hhmmss
format where
hh < 24
. Times are in local time immediately
after the transition. A time interval description consists of a UT offset in
signed +- hh
: mm
:
ss
format, a time zone abbreviation, and an isdst
flag. An abbreviation that equals the UT offset is omitted; other
abbreviations are double-quoted strings unless they consist of one or more
alphabetic characters. An isdst flag is omitted for standard time, and
otherwise is a decimal integer that is unsigned and positive (typically 1)
for daylight saving time and negative for unknown.
In times and in UT offsets with absolute value less than 100 hours, the seconds are omitted if they are zero, and the minutes are also omitted if they are also zero. Positive UT offsets are east of Greenwich. The UT offset -00 denotes a UT placeholder in areas where the actual offset is unspecified; by convention, this occurs when the UT offset is zero and the time zone abbreviation begins with “-” or is “zzz”.
In double-quoted strings, escape sequences represent unusual characters. The escape sequences are \s for space, and \", \\, \f, \n, \r, \t, and \v with their usual meaning in the C programming language. E.g., the double-quoted string ‘CET\s\ \\"’ represents the character sequence ‘CET’
Here is an example of the output, with the leading empty line omitted. (This example is shown with tab stops set far enough apart so that the tabbed columns line up.)
TZ="Pacific/Honolulu"
- | - | -103126 | LMT | |
1896-01-13 | 12:01:26 | -1030 | HST | |
1933-04-30 | 03 | -0930 | HDT | 1 |
1933-05-21 | 11 | -1030 | HST | |
1942-02-09 | 03 | -0930 | HDT | 1 |
1945-08-14 | 13:30 | -0930 | HPT | 1 |
1945-09-30 | 01 | -1030 | HST | |
1947-06-08 | 02:30 | -10 | HST |
Here, local time begins 10 hours, 31 minutes and 26 seconds west of UT, and is a standard time abbreviated LMT. Immediately after the first transition, the date is 1896-01-13 and the time is 12:01:26, and the following time interval is 10.5 hours west of UT, a standard time abbreviated HST. Immediately after the second transition, the date is 1933-04-30 and the time is 03:00:00 and the following time interval is 9.5 hours west of UT, is abbreviated HDT, and is daylight saving time. Immediately after the last transition the date is 1947-06-08 and the time is 02:30:00, and the following time interval is 10 hours west of UT, a standard time abbreviated HST.
Here are excerpts from another example:
TZ="Europe/Astrakhan"
- | - | +031212 | LMT | |
1924-04-30 | 23:47:48 | +03 | ||
1930-06-21 | 01 | +04 | ||
1981-04-01 | 01 | +05 | 1 | |
1981-09-30 | 23 | +04 | ||
... | ||||
2014-10-26 | 01 | +03 | ||
2016-03-27 | 03 | +04 |
This time zone is east of UT, so its UT offsets are positive. Also, many of its time zone abbreviations are omitted since they duplicate the text of the UT offset.
Time discontinuities are found by sampling the results returned by localtime(3) at twelve-hour intervals. This works in all real-world cases; one can construct artificial time zones for which this fails.
In the -v
and -V
output, “UT” denotes the value returned by
gmtime(3), which uses UTC for
modern timestamps and some other UT flavor for timestamps that predate the
introduction of UTC. No attempt is currently made to have the output use
“UTC” for newer and “UT” for older timestamps,
partly because the exact date of the introduction of UTC is problematic.
January 23, 2025 | NetBSD 10.99 |