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    1 ZDUMP(8)                    System Manager's Manual                   ZDUMP(8)
    2 
    3 NAME
    4        zdump - timezone dumper
    5 
    6 SYNOPSIS
    7        zdump [ option ... ] [ timezone ... ]
    8 
    9 DESCRIPTION
   10        The zdump program prints the current time in each timezone named on the
   11        command line.
   12 
   13 OPTIONS
   14        --version
   15               Output version information and exit.
   16 
   17        --help Output short usage message and exit.
   18 
   19        -i     Output a description of time intervals.  For each timezone on
   20               the command line, output an interval-format description of the
   21               timezone.  See "INTERVAL FORMAT" below.
   22 
   23        -v     Output a verbose description of time intervals.  For each
   24               timezone on the command line, print the time at the lowest
   25               possible time value, the time one day after the lowest possible
   26               time value, the times both one second before and exactly at each
   27               detected time discontinuity, the time at one day less than the
   28               highest possible time value, and the time at the highest
   29               possible time value.  Each line is followed by isdst=D where D
   30               is positive, zero, or negative depending on whether the given
   31               time is daylight saving time, standard time, or an unknown time
   32               type, respectively.  Each line is also followed by gmtoff=N if
   33               the given local time is known to be N seconds east of Greenwich.
   34 
   35        -V     Like -v, except omit the times relative to the extreme time
   36               values.  This generates output that is easier to compare to that
   37               of implementations with different time representations.
   38 
   39        -c [loyear,]hiyear
   40               Cut off interval output at the given year(s).  Cutoff times are
   41               computed using the proleptic Gregorian calendar with year 0 and
   42               with Universal Time (UT) ignoring leap seconds.  The lower bound
   43               is exclusive and the upper is inclusive; for example, a loyear
   44               of 1970 excludes a transition occurring at 1970-01-01 00:00:00
   45               UTC but a hiyear of 1970 includes the transition.  The default
   46               cutoff is -500,2500.
   47 
   48        -t [lotime,]hitime
   49               Cut off interval output at the given time(s), given in decimal
   50               seconds since 1970-01-01 00:00:00 Coordinated Universal Time
   51               (UTC).  The timezone determines whether the count includes leap
   52               seconds.  As with -c, the cutoff's lower bound is exclusive and
   53               its upper bound is inclusive.
   54 
   55 INTERVAL FORMAT
   56        The interval format is a compact text representation that is intended
   57        to be both human- and machine-readable.  It consists of an empty line,
   58        then a line "TZ=string" where string is a double-quoted string giving
   59        the timezone, a second line "- - interval" describing the time interval
   60        before the first transition if any, and zero or more following lines
   61        "date time interval", one line for each transition time and following
   62        interval.  Fields are separated by single tabs.
   63 
   64        Dates are in yyyy-mm-dd format and times are in 24-hour hh:mm:ss format
   65        where hh<24.  Times are in local time immediately after the transition.
   66        A time interval description consists of a UT offset in signed +-hhmmss
   67        format, a time zone abbreviation, and an isdst flag.  An abbreviation
   68        that equals the UT offset is omitted; other abbreviations are double-
   69        quoted strings unless they consist of one or more alphabetic
   70        characters.  An isdst flag is omitted for standard time, and otherwise
   71        is a decimal integer that is unsigned and positive (typically 1) for
   72        daylight saving time and negative for unknown.
   73 
   74        In times and in UT offsets with absolute value less than 100 hours, the
   75        seconds are omitted if they are zero, and the minutes are also omitted
   76        if they are also zero.  Positive UT offsets are east of Greenwich.  The
   77        UT offset -00 denotes a UT placeholder in areas where the actual offset
   78        is unspecified; by convention, this occurs when the UT offset is zero
   79        and the time zone abbreviation begins with "-" or is "zzz".
   80 
   81        In double-quoted strings, escape sequences represent unusual
   82        characters.  The escape sequences are \s for space, and \", \\, \f, \n,
   83        \r, \t, and \v with their usual meaning in the C programming language.
   84        E.g., the double-quoted string ""CET\s\"\\"" represents the character
   85        sequence "CET "\".
   86 
   87        Here is an example of the output, with the leading empty line omitted.
   88        (This example is shown with tab stops set far enough apart so that the
   89        tabbed columns line up.)
   90 
   91          TZ="Pacific/Honolulu"
   92          -           -         -103126  LMT
   93          1896-01-13  12:01:26  -1030    HST
   94          1933-04-30  03        -0930    HDT  1
   95          1933-05-21  11        -1030    HST
   96          1942-02-09  03        -0930    HWT  1
   97          1945-08-14  13:30     -0930    HPT  1
   98          1945-09-30  01        -1030    HST
   99          1947-06-08  02:30     -10      HST
  100 
  101        Here, local time begins 10 hours, 31 minutes and 26 seconds west of UT,
  102        and is a standard time abbreviated LMT.  Immediately after the first
  103        transition, the date is 1896-01-13 and the time is 12:01:26, and the
  104        following time interval is 10.5 hours west of UT, a standard time
  105        abbreviated HST.  Immediately after the second transition, the date is
  106        1933-04-30 and the time is 03:00:00 and the following time interval is
  107        9.5 hours west of UT, is abbreviated HDT, and is daylight saving time.
  108        Immediately after the last transition the date is 1947-06-08 and the
  109        time is 02:30:00, and the following time interval is 10 hours west of
  110        UT, a standard time abbreviated HST.
  111 
  112        Here are excerpts from another example:
  113 
  114          TZ="Europe/Astrakhan"
  115          -           -         +031212  LMT
  116          1924-04-30  23:47:48  +03
  117          1930-06-21  01        +04
  118          1981-04-01  01        +05           1
  119          1981-09-30  23        +04
  120          ...
  121          2014-10-26  01        +03
  122          2016-03-27  03        +04
  123 
  124        This time zone is east of UT, so its UT offsets are positive.  Also,
  125        many of its time zone abbreviations are omitted since they duplicate
  126        the text of the UT offset.
  127 
  128 LIMITATIONS
  129        Time discontinuities are found by sampling the results returned by
  130        localtime at twelve-hour intervals.  This works in all real-world
  131        cases; one can construct artificial time zones for which this fails.
  132 
  133        In the -v and -V output, "UT" denotes the value returned by gmtime(3),
  134        which uses UTC for modern timestamps and some other UT flavor for
  135        timestamps that predate the introduction of UTC.  No attempt is
  136        currently made to have the output use "UTC" for newer and "UT" for
  137        older timestamps, partly because the exact date of the introduction of
  138        UTC is problematic.
  139 
  140 SEE ALSO
  141        tzfile(5), zic(8)
  142 
  143                                                                       ZDUMP(8)