ZDUMP(8)                  (2020-04-27)                   ZDUMP(8)

     NAME
          zdump - timezone dumper

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

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

     OPTIONS
          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 lqINTERVAL FORMATrq
               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 sec-
               ond before and exactly at each detected time disconti-
               nuity, the time at one day less than the highest possi-
               ble 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 calen-
               dar 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.

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          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
          The interval format is a compact text representation that is
          intended to be both human- and machine-readable.  It con-
          sists of an empty line, then a line lqTZ=stringrq where string
          is a double-quoted string giving the timezone, a second line
          lq  intervalrq describing the time interval before the first
          transition if any, and zero or more following lines lqdate
          time intervalrq, one line for each transition time and fol-
          lowing 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 immedi-
          ately 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 stan-
          dard 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 unspeci-
          fied; by convention, this occurs when the UT offset is zero
          and the time zone abbreviation begins with lqrq or is lqzzzrq.

          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
          lq"CET\s\"\\"rq represents the character sequence lqCET "\rq.

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          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.  Immedi-
          ately 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 posi-
          tive.  Also, many of its time zone abbreviations are omitted
          since they duplicate the text of the UT offset.

     LIMITATIONS
          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, lqUTrq denotes the value returned by
          gmtime(3), which uses UTC for modern timestamps and some
          other UT flavor for timestamps that predate the introduction

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          of UTC.  No attempt is currently made to have the output use
          lqUTCrq for newer and lqUTrq for older timestamps, partly
          because the exact date of the introduction of UTC is prob-
          lematic.

     SEE ALSO
          tzfile(5), zic(8)

     COLOPHON
          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/.

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