ZIC(8)                    Linux System Administration                   ZIC(8)

       zic - timezone compiler

       zic [ option ... ] [ filename ... ]

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

              Output version information and exit.

       --help Output short usage message and exit.

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

       -l timezone
              Use timezone as local time.  zic will act as if the  input  con-
              tained a link line of the form

                   Link timezone       localtime

       -p timezone
              Use  timezone's  rules when handling POSIX-format timezone envi-
              ronment 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     Be more verbose, and complain about the following situations:

              The input specifies a link to a link.

              A year that appears in a data file is outside the range of years
              representable by time(2) values.

              A time of 24:00 or more appears in the input.  Pre-1998 versions
              of  zic  prohibit  24:00,  and  pre-2007 versions prohibit times
              greater than 24:00.

              A rule goes past the start or end of the month.   Pre-2004  ver-
              sions of zic prohibit this.

              The  output  file does not contain all the information about the
              long-term future of a timezone, 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.

              The output contains data that may not  be  handled  properly  by
              client  code  designed for older zic output formats.  These com-
              patibility issues affect only timestamps before  1970  or  after
              the start of 2038.

              A time zone abbreviation has fewer than 3 characters.  POSIX re-
              quires at least 3.

              An output file name contains a byte that is not an ASCII letter,
              "-", "/", or "_"; or it contains a file name component that con-
              tains more than 14 bytes or that starts with "-".

       -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.

       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) <http://pubs.opengroup.org/
       onlinepubs/9699919799/basedefs/V1_chap06.html>  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  an-
       other  by  one or more white space characters.  The white space charac-
       ters 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.  Nonblank lines are  expected  to
       be of one of three types: rule lines, zone lines, and link lines.

       Names must be in English and are case insensitive.  They appear in sev-
       eral contexts, and include month and weekday names and keywords such as
       maximum,  only,  Rolling, and Zone.  A name can be abbreviated by omit-
       ting all but an initial prefix; any abbreviation 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  2:00w  1:00   D

       The fields that make up a rule line are:

       NAME    Gives  the  name  of the rule set that contains this line.  The
               name must start with a character that is neither an ASCII digit
               nor  "-"  nor "+".  To allow for future extensions, an unquoted
               name   should   not   contain   characters   from    the    set

       FROM    Gives the first year in which the rule applies.  Any signed in-
               teger year can be supplied; the proleptic Gregorian calendar is
               assumed, with year 0 preceding year 1.  The word minimum (or an
               abbreviation) means the indefinite past.  The word maximum  (or
               an  abbreviation)  means  the indefinite future.  Rules can de-
               scribe times that are not representable as  time  values,  with
               the unrepresentable times ignored; this allows rules to be por-
               table 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 abbrevia-
               tion) may be used to repeat the value of the FROM field.

       TYPE    should be "-" and is present for compatibility with older  ver-
               sions 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

                    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

               A  weekday  name  (e.g.,  Sunday) or a weekday name preceded by
               "last" (e.g., lastSunday) 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.  Recog-
               nized forms include:

                    2            time in hours
                    2:00         time in hours and minutes
                    01:28:14     time in hours, minutes, and seconds
                    15:00        24-hour format time (for times after noon)
                    260:00       260 hours after 00:00
                    -2:30        2.5 hours before 00:00
                    -            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).   Negative offsets are allowed; in Ireland, for example,
               daylight saving time is observed in winter and has  a  negative
               offset  relative  to Irish Standard Time.  The offset is merely
               added to standard time; 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.

               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        UTOFF  RULES   FORMAT  [UNTIL]

       For example:

            Zone  Asia/Amman  2:00   Jordan  EE%sT   2017 Oct 27 01:00

       The fields that make up a zone line are:

       NAME The name of the timezone.  This is the name used in  creating  the
            time  conversion information file for the timezone.  It should not
            contain a file name component "." or ".."; a file  name  component
            is a maximal substring that does not contain "/".

            The  amount of time to add to UT to get standard time.  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.

            The  name  of  the  rules  that apply in the timezone or, alterna-
            tively, a field in the same format as  a  rule-line  SAVE  column,
            giving  of  the  amount of time to be added to local standard time
            effect, and whether the resulting time  is  standard  or  daylight
            saving.   If  this  field  is - then standard time always applies.
            When an amount of time is given, only the sum of standard time and
            this amount matters.

            The format for time zone abbreviations.  The pair of characters %s
            is used to show where the "variable part" of the time zone  abbre-
            viation goes.  Alternatively, a format can use the pair of charac-
            ters %z to stand for the UT 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 UT.  Alternatively, a slash (/) separates standard
            and daylight abbreviations.  To conform to POSIX, a time zone  ab-
            breviation  should contain only alphanumeric ASCII characters, "+"
            and "-".

            The time at which the UT offset or the rule(s) change for a  loca-
            tion.  It takes the form of YEAR [MONTH [DAY [TIME]]].  If this is
            specified, the time zone information is generated from  the  given
            UT  offset  and rule change until the time specified, which is in-
            terpreted 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 field.

       Except for continuation lines, lines may appear in any order in the in-
       put.   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  2016  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.  In this example, the EU rules are  for  the  European
       Union and for its predecessor organization, the European Communities.

         # 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  NAME           UTOFF    RULES  FORMAT  [UNTIL]
         Zone    Europe/Zurich  0:34:08  -      LMT     1853 Jul 16
                                0:29:46  -      BMT     1894 Jun
                                1:00     Swiss  CE%sT   1981
                                1:00     EU     CE%sT

         Link    Europe/Zurich  Europe/Vaduz

       In  this  example,  the  timezone  is named Europe/Zurich but it has an
       alias as Europe/Vaduz.  This example says that Zurich  was  34  minutes
       and 8 seconds east of UT until 1853-07-16 at 00:00, when the legal off-
       set was changed to 7<degree>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 the UT  offset  became  one
       hour and Swiss daylight saving rules (defined with lines beginning with
       "Rule Swiss") apply.  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 com-
       pleteness.  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, respec-
       tively.  Since Swiss rules and later EU rules were  applied,  the  time
       zone  abbreviation has been CET for standard time and CEST for daylight
       saving time.

              Default local timezone file.

              Default timezone information directory.

       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  com-
       piled file is correct.

       If,  for  a particular timezone, 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 speci-
       fying transition instants using universal time.

       tzfile(5), zdump(8)

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                                  2019-03-06                            ZIC(8)
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