zdump(8) — Linux manual page

NAME | SYNOPSIS | DESCRIPTION | OPTIONS | INTERVAL FORMAT | LIMITATIONS | SEE ALSO | COLOPHON

ZDUMP(8)               Linux System Administration              ZDUMP(8)

NAME         top

       zdump - timezone dumper

SYNOPSIS         top

       zdump [ option ... ] [ timezone ... ]

DESCRIPTION         top

       The zdump program prints the current time in each timezone named
       on the command line.

OPTIONS         top

       --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 time at the lowest
              possible time value, the time one day after the lowest
              possible time value, the times both one second before and
              exactly at each detected time discontinuity, the time at
              one day less than the highest possible time value, and the
              time at the highest possible time value.  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 the times relative to the extreme
              time 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 exclusive and the upper is
              inclusive; for example, -c 1970,2070 selects transitions
              after 1970-01-01 00:00:00 UTC and on or 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 exclusive and its upper bound is inclusive.

INTERVAL FORMAT         top

       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.

LIMITATIONS         top

       Time discontinuities are found by sampling the results returned
       by localtime 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.

SEE ALSO         top

       tzfile(5), zic(8)

COLOPHON         top

       This page is part of release 5.10 of the Linux man-pages project.
       A description of the project, information about reporting bugs,
       and the latest version of this page, can be found at
       https://www.kernel.org/doc/man-pages/.

                               2020-04-27                       ZDUMP(8)

Pages that refer to this page: tzfile(5)tzselect(8)zic(8)