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

     zic - time zone compiler

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

     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 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.
     -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
     -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.
     -v          Be more verbose, and complain about the following situations:



                 -   Pre-1998 versions of zic(8) prohibit 24:00, and pre-2007
                     versions prohibit times greater than 24:00.

                 -   Pre-2004 versions of zic(8) prohibit this.

                 -   long-term future of a zone, because the future cannot be
                     summarized as an extended POSIX TZ string.  For example,
                     as of 2013 this problem occurs for Iran's daylight-saving
                     rules for the predicted future, as these rules are based
                     on the Iranian calendar, which cannot be represented.

                 -   code designed for older zic(8) output formats.  These
                     compatibility issues affect only time stamps before 1970
                     or after the start of 2038.

                 -   POSIX requires at least 3.

                 -   "-", "/", or "_"; or it or it contains a file name
                     component that contains more than 14 bytes or that starts
                     with "-".

                 Input files should be text files, that is, they should be a
                 series of zero or more lines, each ending in a newline byte
                 and containing at most 511 bytes, and without any NUL bytes.
                 The input text's encoding is typically UTF-8 or ASCII; it
                 should have a unibyte representation for the POSIX Portable
                 Character Set (PPCS)
                 and the encoding's non-unibyte characters should consist
                 entirely of non-PPCS bytes.  Non-PPCS characters typically
                 occur only in comments: although output file names and time
                 zone abbreviations can contain nearly any character, other
                 software will work better if these are limited to the
                 restricted syntax described under the [v] option.

                 Input lines are made up of fields.  Fields are separated from
                 one another by one or more white space characters.  The white
                 space characters are space, form feed, carriage return,
                 newline, tab, and vertical tab.  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

                 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 proleptic
                           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      should be "-" and is present for compatibility with
                           older versions of zic in which it could contain
                           year types.
                 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
                                 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.  The intent is that a rule line describes
                           the instants when a clock/calendar set to the type
                           of time specified in the AT field would show the
                           specified date and time of day.
                 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).  Only the sum of standard time and this
                           amount matters; for example, zic does not
                           distinguish a 10:30 standard time plus an 0:30 SAVE
                           from a 10:00 standard time plus a 1:00 SAVE.
                 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  AC%sT     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.  It should not contain a file name
                             component "".  or ".."; a file name component is
                             a maximal substring that does not contain "/".
                 GMTOFF      The amount of time to add to UT 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 UT.
                 RULES/SAVE  The name of the rule(s) that apply in the time
                             zone or, alternatively, an amount of time to add
                             to local standard time.  If this field is - then
                             standard time always applies in the time zone.
                             When an amount of time is given, only the sum of
                             standard time and this amount matters.
                 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 format can use
                             the pair of characters %z +to stand for the UTC
                             offset in the form +- hh, +- hhmm, or +- hhmmss,
                             using the shortest form that does not lose
                             information, where hh, mm, and ss are the hours,
                             minutes, and seconds east (+) or west (-) of UTC.
                             Alternatively, a slash (/) separates standard and
                             daylight abbreviations.  To conform to POSIX, a
                             time zone abbreviation should contain only
                             alphanumeric ASCII characters, "+" and "".
                 UNTILYEAR [MONTH [DAY [TIME]]]
                             The time at which the UT 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 UT offset and rule
                             change until the time specified, which is
                             interpreted using the rules in effect just before
                             the transition.  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.

                 If a zone changes at the same instant that a rule would
                 otherwise take effect in the earlier zone or continuation
                 line, the rule is ignored.  In a single zone it is an error
                 if two rules take effect at the same instant, or if two zone
                 changes take effect at the same instant.

                 A link line has the form
                       Link TARGET    LINK-NAME
                 For example:
                       Link Europe/Istanbul     Asia/Istanbul
                 The TARGET field should appear as the NAME field in some zone
                 line.  The LINK-NAME field is used as an alternative name for
                 that zone; it has the same syntax as a zone line's NAME

                 Except for continuation lines, lines may appear in any order
                 in the input.  However, the behavior is unspecified if
                 multiple zone or link lines define the same name, or if the
                 source of one link line is the target of another.

                 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.

     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 1941 1942 -    May Mon>=1  1:00  1:00 S
     Rule   Swiss 1941 1942 -    Oct Mon>=1  2:00  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   Europe/Zurich 0:34:08 -          LMT    1853 Jul 16
                          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.  This example says that Zurich was 34 minutes and 8 seconds
     west of UT until 1853-07-16 at 00:00, when the legal offset was changed
     to 7<deg>26'22.50''; although this works out to 0:29:45.50, the input
     format cannot represent fractional seconds so it is rounded here.  After
     1894-06-01 at 00:00 Swiss daylight saving rules (defined with lines
     beginning with "Rule Swiss") apply, and the UT 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 1941 and 1942, daylight saving time applied from the first Monday in
     May at 01:00 to the first Monday in October at 02:00.  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

     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 time zone has been CET for standard time and CEST
     for daylight saving time.

     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 UT offset, zic produces a single transition to daylight
     saving at the new UT offset (without any change in wall clock time).  To
     get separate transitions use multiple zone continuation lines specifying
     transition instants using universal time.

     Time stamps well before the Big Bang are silently omitted from the
     output.  This works around bugs in software that mishandles large
     negative time stamps.  Call it sour grapes, but pre-Big-Bang time stamps
     are physically suspect anyway.  The pre-Big-Bang cutoff time is
     approximate and may change in future versions.

     /usr/share/zoneinfo - standard directory used for created files

     ctime(3), tzfile(5), zdump(8)

NetBSD 8.0                      August 13, 2015                     NetBSD 8.0