ZIC(8)                                                                  ZIC(8)

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)

                                                                        ZIC(8)
