zdump(8) — Linux manual page


zdump(8)                 System Manager's Manual                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 times at the two
              extreme time values, the times (if present) at and just
              beyond the boundaries of years that localtime(3) and
              gmtime(3) can represent, and the times both one second
              before and exactly at each detected time discontinuity.
              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 output concerning extreme time and
              year values.  This generates output that is easier to
              compare to that of implementations with different time

       -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 inclusive and the upper is
              exclusive; for example, -c 1970,2070 selects transitions
              on or after 1970-01-01 00:00:00 UTC and 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 inclusive and its upper bound is exclusive.


       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.)

         -           -         -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(3) 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)

Time Zone Database                                              zdump(8)

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