ZDUMP(8)                    System Manager's Manual                   ZDUMP(8)

NAME
       zdump - time zone dumper

SYNOPSIS
       zdump [ option ... ] [ zonename ... ]

DESCRIPTION
       Zdump prints the current time in each zonename named on the command
       line.

       These options are available:

       --version
              Output version information and exit.

       -i     (This option is experimental: its behavior may change in future
              versions.)  Output a description of time intervals.  For each
              zonename on the command line, output an interval-format
              description of the zone.  See "INTERVAL FORMAT" below.

       -v     Output a verbose description of time intervals.  For each
              zonename 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.  The lower bound
              is exclusive and the upper is inclusive; for example, a loyear
              of 1970 excludes a transition occurring at 1970-01-01 00:00:00
              UTC but a hiyear of 1970 includes the transition.  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 zonename 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
       This format is experimental: it may change in future versions.

       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 zone name, 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"
         -          -          -10:31:26  LMT
         1896-01-13 12:01:26   -10:30     HST
         1933-04-30 03         -09:30     HDT        1
         1933-05-21 11         -10:30     HST
         1942-02-09 03         -09:30     HDT        1
         1945-09-30 01         -10:30     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"
         -          -          +03:12:12  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
       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 time stamps and some other UT flavor for time
       stamps that predate the introduction of UTC.  No attempt is currently
       made to have the output use "UTC" for newer and "UT" for older time
       stamps, partly because the exact date of the introduction of UTC is
       problematic.

SEE ALSO
       newctime(3), tzfile(5), zic(8)

                                                                      ZDUMP(8)
