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NAME | SYNOPSIS | DESCRIPTION | OPTIONS | INTERVAL FORMAT | LIMITATIONS | SEE ALSO | COLOPHON |
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zdump(8) System Manager's Manual zdump(8)
zdump - timezone dumper
zdump [ option ... ] [ timezone ... ]
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
Output version information and exit.
--help Output short usage message and exit.
-i Output a description of time intervals. For each timezone
on the command line, output an interval-format description
of the timezone. See “INTERVAL FORMAT” below.
-v Output a verbose description of time intervals. For each
timezone on the command line, print the times at the two
extreme time values, the times (if present) at and just
beyond the boundaries of years that localtime(3) and
gmtime(3) can represent, and the times both one second
before and exactly at each detected time discontinuity.
Each line is followed by isdst=D where D is positive, zero,
or negative depending on whether the given time is daylight
saving time, standard time, or an unknown time type,
respectively. Each line is also followed by gmtoff=N if
the given local time is known to be N seconds east of
Greenwich.
-V Like -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.
-c [loyear,]hiyear
Cut off interval output at the given year(s). Cutoff times
are computed using the proleptic Gregorian calendar with
year 0 and with Universal Time (UT) ignoring leap seconds.
Cutoffs are at the start of each year, where the lower-
bound timestamp is inclusive and the upper is exclusive;
for example, -c 1970,2070 selects transitions on or after
1970-01-01 00:00:00 UTC and before 2070-01-01 00:00:00 UTC.
The default cutoff is -500,2500.
-t [lotime,]hitime
Cut off interval output at the given time(s), given in
decimal seconds since 1970-01-01 00:00:00 Coordinated
Universal Time (UTC). The timezone determines whether the
count includes leap seconds. As with -c, the cutoff's
lower bound is inclusive and its upper bound is exclusive.
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 hh:mm:ss
format where hh<24. Times are in local time immediately after the
transition. A time interval description consists of a UT offset
in signed ±hhmmss 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 HWT 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.
tzfile(5), zic(8)
This page is part of the man-pages (Linux kernel and C library
user-space interface documentation) project. Information about
the project can be found at
⟨https://www.kernel.org/doc/man-pages/⟩. If you have a bug report
for this manual page, see
⟨https://git.kernel.org/pub/scm/docs/man-pages/man-pages.git/tree/CONTRIBUTING⟩.
This page was obtained from the tarball man-pages-6.15.tar.gz
fetched from
⟨https://mirrors.edge.kernel.org/pub/linux/docs/man-pages/⟩ on
2025-08-11. If you discover any rendering problems in this HTML
version of the page, or you believe there is a better or more up-
to-date source for the page, or you have corrections or
improvements to the information in this COLOPHON (which is not
part of the original manual page), send a mail to
[email protected]
Time Zone Database zdump(8)
Pages that refer to this page: tzfile(5), tzselect(8), zic(8)
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HTML rendering created 2025-09-06 by Michael Kerrisk, author of The Linux Programming Interface. For details of in-depth Linux/UNIX system programming training courses that I teach, look here. Hosting by jambit GmbH. |
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