zdump

ZDUMP(8)                  Linux System Administration                 ZDUMP(8)

NAME
       zdump - timezone dumper

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

DESCRIPTION
       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 "INTERVAL FORMAT" below.

       -v     Output a verbose description of time intervals.  For each  time-
              zone  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 de-
              tected time discontinuity, the time at one  day  less  than  the
              highest  possible time value, and the time at the highest possi-
              ble 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 val-
              ues.  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 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 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 charac-
       ters.  An isdst flag is omitted for standard time, and otherwise  is  a
       decimal  integer  that  is unsigned and positive (typically 1) for day-
       light 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 charac-
       ters.  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  ab-
       breviated  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  lo-
       caltime  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 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
       tzfile(5), zic(8)

COLOPHON
       This  page  is  part of release 5.05 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/.

                                  2019-03-06                          ZDUMP(8)