zdump

ZDUMP(8)                     System Manager's Manual                    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 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.

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 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"
         -           -         -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:

         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 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 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
       tzfile(5), zic(8)



                                                                        ZDUMP(8)