Updated: 2021/Apr/14

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

     zdump - timezone dumper

     zdump [--version] [-v] [-V] [-c [loyear,]highyear] [timezone ...]
     zdump -t [lotime,]hightime [zonename ...]

     The zdump program prints the current time in each timezone named on the
     command line.
     --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
                timezon 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.
     -c [loyear,]highyear
                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,]hightime
                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.
     -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.

     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 hhmmss format
     where hh < 24.  Times are in local time immediately after the transition.
     A time interval description consists of a UT offset in signed +- hh: mm:
     ss 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     HDT   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.

     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

     tzfile(5), zic(8)

NetBSD 9.99                      May 25, 2020                      NetBSD 9.99