zdump(8) — Linux manual page


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

              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.


       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

       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.)

         -           -         -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:

         -           -         +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 5.08 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

                                 2020-04-27                         ZDUMP(8)

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