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

NAME
     zdump -- timezone dumper

SYNOPSIS
     zdump [--help] [--version] [-ivV] [-c [loyear,]hiyear] [-t [lotime,]hitime]
	   [timezone ...]

DESCRIPTION
     The  zdump  program  prints  the current time in each timezone named on the
     command line.  A timezone of - is treated as if it  were  /dev/stdin;  this
     can be used to pipe TZif data into zdump.

     The following options are available:

     --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  time-
	     zone.  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  val-
	     ues,  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 disconti-
	     nuity.  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 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.  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 sec-
	     onds 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.

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  time-
     zone,  a second line "- - interval" describing the time interval before the
     first transition if any, and zero or more following lines "date time inter-
     val", 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 ab-
     breviation 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 deci-
     mal 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 un-
     specified; 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  transi-
     tion,  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  local-
     time(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 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 timestamps,
     partly because the exact date of the introduction of UTC is problematic.

SEE ALSO
     tzfile(5), zic(8)

FreeBSD 15.1			December 15, 2022			ZDUMP(8)
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