NAME

     zic - time zone compiler

SYNOPSIS
     zic [ --version ] [ -v ] [ -d directory ] [ -l localtime ] [
     -p posixrules ] [ -L leapsecondfilename ] [ -s ] [ -y
     command ] [ filename ... ]

DESCRIPTION
     Zic reads text from the file(s) named on the command line
     and creates the time conversion information files specified
     in this input.  If a filename is -, the standard input is
     read.

     These options are available:

     --version
          Output version information and exit.

     -d directory
          Create time conversion information files in the named
          directory rather than in the standard directory named
          below.

     -l timezone
          Use the given time zone as local time.  Zic will act as
          if the input contained a link line of the form

               Link timezone       localtime

     -p timezone
          Use the given time zone's rules when handling POSIX-
          format time zone environment variables.  Zic will act
          as if the input contained a link line of the form

               Link timezone       posixrules

     -L leapsecondfilename
          Read leap second information from the file with the
          given name.  If this option is not used, no leap second
          information appears in output files.

     -v   Complain if a year that appears in a data file is
          outside the range of years representable by time(2)
          values.  Also complain if a time of 24:00 (which cannot
          be handled by pre-1998 versions of zic) appears in the
          input.

     -s   Limit time values stored in output files to values that
          are the same whether they're taken to be signed or
          unsigned.  You can use this option to generate SVVS-
          compatible files.

     -y command
          Use the given command rather than yearistype when
          checking year types (see below).

     Input lines are made up of fields.  Fields are separated
     from one another by any number of white space characters.
     Leading and trailing white space on input lines is ignored.
     An unquoted sharp character (#) in the input introduces a
     comment which extends to the end of the line the sharp
     character appears on.  White space characters and sharp
     characters may be enclosed in double quotes (") if they're
     to be used as part of a field.  Any line that is blank
     (after comment stripping) is ignored.  Non-blank lines are
     expected to be of one of three types: rule lines, zone
     lines, and link lines.

     Names (such as month names) must be in English and are case
     insensitive.  Abbreviations, if used, must be unambiguous in
     context.

     A rule line has the form

          Rule  NAME  FROM  TO    TYPE  IN   ON       AT    SAVE  LETTER/S

     For example:

          Rule  US    1967  1973  -     Apr  lastSun  2:00  1:00  D

     The fields that make up a rule line are:

     NAME    Gives the (arbitrary) name of the set of rules this
             rule is part of.

     FROM    Gives the first year in which the rule applies.  Any
             integer year can be supplied; the Gregorian calendar
             is assumed.  The word minimum (or an abbreviation)
             means the minimum year representable as an integer.
             The word maximum (or an abbreviation) means the
             maximum year representable as an integer.  Rules can
             describe times that are not representable as time
             values, with the unrepresentable times ignored; this
             allows rules to be portable among hosts with
             differing time value types.

     TO      Gives the final year in which the rule applies.  In
             addition to minimum and maximum (as above), the word
             only (or an abbreviation) may be used to repeat the
             value of the FROM field.

     TYPE    Gives the type of year in which the rule applies.
             If TYPE is - then the rule applies in all years
             between FROM and TO inclusive.  If TYPE is something
             else, then zic executes the command
                  yearistype year type
             to check the type of a year: an exit status of zero
             is taken to mean that the year is of the given type;
             an exit status of one is taken to mean that the year
             is not of the given type.

     IN      Names the month in which the rule takes effect.
             Month names may be abbreviated.

     ON      Gives the day on which the rule takes effect.
             Recognized forms include:

                  5        the fifth of the month
                  lastSun  the last Sunday in the month
                  lastMon  the last Monday in the month
                  Sun>=8   first Sunday on or after the eighth
                  Sun<=25  last Sunday on or before the 25th

             Names of days of the week may be abbreviated or
             spelled out in full.  Note that there must be no
             spaces within the ON field.

     AT      Gives the time of day at which the rule takes
             effect.  Recognized forms include:

                  2        time in hours
                  2:00     time in hours and minutes
                  15:00    24-hour format time (for times after noon)
                  1:28:14  time in hours, minutes, and seconds
                  -        equivalent to 0

             where hour 0 is midnight at the start of the day,
             and hour 24 is midnight at the end of the day.  Any
             of these forms may be followed by the letter w if
             the given time is local "wall clock" time, s if the
             given time is local "standard" time, or u (or g or
             z) if the given time is universal time; in the
             absence of an indicator, wall clock time is assumed.

     SAVE    Gives the amount of time to be added to local
             standard time when the rule is in effect.  This
             field has the same format as the AT field (although,
             of course, the w and s suffixes are not used).

     LETTER/S
             Gives the "variable part" (for example, the "S" or
             "D" in "EST" or "EDT") of time zone abbreviations to
             be used when this rule is in effect.  If this field
             is -, the variable part is null.

     A zone line has the form

          Zone  NAME                GMTOFF  RULES/SAVE  FORMAT  [UNTILYEAR [MONTH [DAY [TIME]]]]

     For example:

          Zone  Australia/Adelaide  9:30    Aus         CST     1971 Oct 31 2:00

     The fields that make up a zone line are:

     NAME  The name of the time zone.  This is the name used in
           creating the time conversion information file for the
           zone.

     GMTOFF
           The amount of time to add to UTC to get standard time
           in this zone.  This field has the same format as the
           AT and SAVE fields of rule lines; begin the field with
           a minus sign if time must be subtracted from UTC.

     RULES/SAVE
           The name of the rule(s) that apply in the time zone
           or, alternately, an amount of time to add to local
           standard time.  If this field is - then standard time
           always applies in the time zone.

     FORMAT
           The format for time zone abbreviations in this time
           zone.  The pair of characters %s is used to show where
           the "variable part" of the time zone abbreviation
           goes.  Alternately, a slash (/) separates standard and
           daylight abbreviations.

     UNTILYEAR [MONTH [DAY [TIME]]]
           The time at which the UTC offset or the rule(s) change
           for a location.  It is specified as a year, a month, a
           day, and a time of day.  If this is specified, the
           time zone information is generated from the given UTC
           offset and rule change until the time specified.  The
           month, day, and time of day have the same format as
           the IN, ON, and AT fields of a rule; trailing fields
           can be omitted, and default to the earliest possible
           value for the missing fields.

           The next line must be a "continuation" line; this has
           the same form as a zone line except that the string
           "Zone" and the name are omitted, as the continuation
           line will place information starting at the time
           specified as the "until" information in the previous
           line in the file used by the previous line.
           Continuation lines may contain "until" information,
           just as zone lines do, indicating that the next line
           is a further continuation.

     A link line has the form

          Link  LINK-FROM        LINK-TO

     For example:

          Link  Europe/Istanbul  Asia/Istanbul

     The LINK-FROM field should appear as the NAME field in some
     zone line; the LINK-TO field is used as an alternate name
     for that zone.

     Except for continuation lines, lines may appear in any order
     in the input.

     Lines in the file that describes leap seconds have the
     following form:

          Leap  YEAR  MONTH  DAY  HH:MM:SS  CORR  R/S

     For example:

          Leap  1974  Dec    31   23:59:60  +     S

     The YEAR, MONTH, DAY, and HH:MM:SS fields tell when the leap
     second happened.  The CORR field should be "+" if a second
     was added or "-" if a second was skipped.  The R/S field
     should be (an abbreviation of) "Stationary" if the leap
     second time given by the other fields should be interpreted
     as UTC or (an abbreviation of) "Rolling" if the leap second
     time given by the other fields should be interpreted as
     local wall clock time.

EXTENDED EXAMPLE
     Here is an extended example of zic input, intended to
     illustrate many of its features.

       # Rule  NAME  FROM  TO    TYPE  IN   ON       AT    SAVE  LETTER/S
       Rule    Swiss 1940  only  -     Nov  2        0:00  1:00  S
       Rule    Swiss 1940  only  -     Dec  31       0:00  0     -
       Rule    Swiss 1941  1942  -     May  Sun>=1   2:00  1:00  S
       Rule    Swiss 1941  1942  -     Oct  Sun>=1   0:00  0
       Rule    EU    1977  1980  -     Apr  Sun>=1   1:00u 1:00  S
       Rule    EU    1977  only  -     Sep  lastSun  1:00u 0     -
       Rule    EU    1978  only  -     Oct   1       1:00u 0     -
       Rule    EU    1979  1995  -     Sep  lastSun  1:00u 0     -
       Rule    EU    1981  max   -     Mar  lastSun  1:00u 1:00  S
       Rule    EU    1996  max   -     Oct  lastSun  1:00u 0     -

       # Zone  NAME           GMTOFF   RULES       FORMAT  UNTIL
       Zone    Europe/Zurich  0:34:08  -           LMT     1848 Sep 12
                              0:29:44  -           BMT     1894 Jun
                              1:00     Swiss       CE%sT   1981
                              1:00     EU          CE%sT

       Link    Europe/Zurich  Switzerland

     In this example, the zone is named Europe/Zurich but it has
     an alias as Switzerland.  Zurich was 34 minutes and 8
     seconds west of GMT until 1848-09-12 at 00:00, when the
     offset changed to 29 minutes and 44 seconds.  After
     1894-06-01 at 00:00 Swiss daylight saving rules (defined
     with lines beginning with "Rule Swiss") apply, and the GMT
     offset became one hour.  From 1981 to the present, EU
     daylight saving rules have applied, and the UTC offset has
     remained at one hour.

     In 1940, daylight saving time applied from November 2 at
     00:00 to December 31 at 00:00.  In 1941 and 1942, daylight
     saving time applied from the first Sunday in May at 02:00 to
     the first Sunday in October at 00:00.  The pre-1981 EU
     daylight-saving rules have no effect here, but are included
     for completeness.  Since 1981, daylight saving has begun on
     the last Sunday in March at 01:00 UTC.  Until 1995 it ended
     the last Sunday in September at 01:00 UTC, but this changed
     to the last Sunday in October starting in 1996.

     For purposes of display, "LMT" and "BMT" were initially
     used, respectively.  Since Swiss rules and later EU rules
     were applied, the display name for the timezone has been CET
     for standard time and CEST for daylight saving time.

NOTES
     For areas with more than two types of local time, you may
     need to use local standard time in the AT field of the
     earliest transition time's rule to ensure that the earliest
     transition time recorded in the compiled file is correct.

     If, for a particular zone, a clock advance caused by the
     start of daylight saving coincides with and is equal to a
     clock retreat caused by a change in UTC offset, zic produces
     a single transition to daylight saving at the new UTC offset
     (without any change in wall clock time).  To get separate
     transitions use multiple zone continuation lines specifying
     transition instants using universal time.

FILE
     /usr/local/etc/zoneinfo         standard directory used for
     created files

SEE ALSO
     newctime(3), tzfile(5), zdump(8)
