ZIC(8)                    (2020-08-13)                     ZIC(8)

     NAME
          zic - timezone compiler

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

     DESCRIPTION
          The zic program 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 lq-rq, stan-
          dard input is read.

     OPTIONS
          --version
               Output version information and exit.

          --help
               Output short usage message and exit.

          -b bloat
               Output backward-compatibility data as specified by
               bloat. If bloat is fat, generate additional data
               entries that work around potential bugs or incompati-
               bilities in older software, such as software that mis-
               handles the 64-bit generated data.  If bloat is slim,
               keep the output files small; this can help check for
               the bugs and incompatibilities.  Although the default
               is currently fat, this is intended to change in future
               zic versions, as software that mishandles the 64-bit
               data typically mishandles timestamps after the year
               2038 anyway.  Also see the -r option for another way to
               shrink output size.

          -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 contained a link line of the form

                    Link  timezone  localtime

          -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.

          -p timezone

     Page 1                       Plan 9             (printed 5/24/22)

     ZIC(8)                    (2020-08-13)                     ZIC(8)

               Use timezone's rules when handling nonstandard TZ
               strings like "EET-2EEST" that lack transition rules.
               zic will act as if the input contained a link line of
               the form

                    Link  timezone  posixrules

               This feature is obsolete and poorly supported.  Among
               other things it should not be used for timestamps after
               the year 2037, and it should not be combined with -b
               slim if timezone's transitions are at standard time or
               Universal Time (UT) instead of local time.

          -r [@lo][/@hi]
               Reduce the size of output files by limiting their
               applicability to timestamps in the range from lo
               (inclusive) to hi (exclusive), where lo and hi are
               possibly-signed decimal counts of seconds since the
               Epoch (1970-01-01 00:00:00 UTC).  Omitted counts
               default to extreme values.  For example, lqzic -r @0rq
               omits data intended for negative timestamps (i.e.,
               before the Epoch), and lqzic -r @0/@2147483648rq outputs
               data intended only for nonnegative timestamps that fit
               into 31-bit signed integers.  On platforms with GNU
               date, lqzic -r @$(date +%s)rq omits data intended for
               past timestamps.  Also see the -b slim option for
               another way to shrink output size.

          -t file
               When creating local time information, put the configu-
               ration link in the named file rather than in the stan-
               dard location.

          -v   Be more verbose, and complain about the following situ-
               ations:

               The input specifies a link to a link.

               A year that appears in a data file is outside the range
               of representable years.

               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 versions of zic prohibit this.

               A time zone abbreviation uses a %z format.  Pre-2015
               versions of zic do not support this.

               A timestamp contains fractional seconds.  Pre-2018

     Page 2                       Plan 9             (printed 5/24/22)

     ZIC(8)                    (2020-08-13)                     ZIC(8)

               versions of zic do not support this.

               The input contains abbreviations that are mishandled by
               pre-2018 versions of zic due to a longstanding coding
               bug.  These abbreviations include lqLrq for lqLinkrq, lqmirq
               for lqminrq, lqSarq for lqSatrq, and lqSurq for lqSunrq.

               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 2019 this problem occurs
               for Iran's daylight-saving rules for the predicted
               future, as these rules are based on the Iranian calen-
               dar, which cannot be represented.

               The output contains data that may not be handled prop-
               erly by client code designed for older zic output for-
               mats.  These compatibility issues affect only times-
               tamps before 1970 or after the start of 2038.

               The output file contains more than 1200 transitions,
               which may be mishandled by some clients.  The current
               reference client supports at most 2000 transitions;
               pre-2014 versions of the reference client support at
               most 1200 transitions.

               A time zone abbreviation has fewer than 3 or more than
               6 characters.  POSIX requires at least 3, and requires
               implementations to support at least 6.

               An output file name contains a byte that is not an
               ASCII letter, lq-rq, lq/rq, or lq_rq; or it contains a file
               name component that contains more than 14 bytes or that
               starts with lq-rq.

     FILES
          Input files use the format described in this section; output
          files use tzfile(5) format.

          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)
          lahttp://pubs.opengroup.org/onlinepubs/9699919799/basedefs/V1_chap06.htmlra
          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.

     Page 3                       Plan 9             (printed 5/24/22)

     ZIC(8)                    (2020-08-13)                     ZIC(8)

          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 trail-
          ing 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 strip-
          ping) 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 several contexts, and include month and weekday
          names and keywords such as maximum, only, Rolling, and Zone.
          A name can be abbreviated by omitting all but an initial
          prefix; any abbreviation 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  2:00w  1:00d  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 lq-rq nor lq+rq.  To allow
                  for future extensions, an unquoted name should not
                  contain characters from the set
                  lq!$%&'()*,/:;<=>?@[\]ha`{|}tirq.

          FROM    Gives the first year in which the rule applies.  Any
                  signed integer 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 abbre-
                  viation) means the indefinite future.  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 differ-
                  ing 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.

     Page 4                       Plan 9             (printed 5/24/22)

     ZIC(8)                    (2020-08-13)                     ZIC(8)

          TYPE    should be lq-rq 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.  Rec-
                  ognized 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

                  A weekday name (e.g., Sunday) or a weekday name pre-
                  ceded by lqlastrq (e.g., lastSunday) may be abbrevi-
                  ated or spelled out in full.  There must be no white
                  space characters within the ON field.  The lq<=rq and
                  lq>=rq constructs can result in a day in the neighbor-
                  ing month; for example, the IN-ON combination lqOct
                  Sun>=31rq stands for the first Sunday on or after
                  October 31, even if that Sunday occurs in November.

          AT      Gives the time of day at which the rule takes
                  effect, relative to 00:00, the start of a calendar
                  day.  Recognized forms include:

                       2            time in hours
                       2:00         time in hours and minutes
                       01:28:14     time in hours, minutes, and seconds
                       00:19:32.13  time with fractional seconds
                       12:00        midday, 12 hours after 00:00
                       15:00        3 PM, 15 hours after 00:00
                       24:00        end of day, 24 hours after 00:00
                       260:00       260 hours after 00:00
                       -2:30        2.5 hours before 00:00
                       -            equivalent to 0

                  Although zic rounds times to the nearest integer
                  second (breaking ties to the even integer), the
                  fractions may be useful to other applications
                  requiring greater precision.  The source format does
                  not specify any maximum precision.  Any of these
                  forms may be followed by the letter w if the given
                  time is local or lqwall clockrq time, s if the given
                  time is standard time without any adjustment for
                  daylight saving, or u (or g or z) if the given time
                  is universal time; in the absence of an indicator,
                  local (wall clock) time is assumed.  These forms
                  ignore leap seconds; for example, if a leap second

     Page 5                       Plan 9             (printed 5/24/22)

     ZIC(8)                    (2020-08-13)                     ZIC(8)

                  occurs at 00:59:60 local time, lq1:00rq stands for
                  3601 seconds after local midnight instead of the
                  usual 3600 seconds.  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 stan-
                  dard time when the rule is in effect, and whether
                  the resulting time is standard or daylight saving.
                  This field has the same format as the AT field
                  except with a different set of suffix letters: s for
                  standard time and d for daylight saving time.  The
                  suffix letter is typically omitted, and defaults to
                  s if the offset is zero and to d otherwise.  Nega-
                  tive 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.

          LETTER/S
                  Gives the lqvariable partrq (for example, the lqSrq or
                  lqDrq in lqESTrq or lqEDTrq) of time zone abbreviations to
                  be used when this rule is in effect.  If this field
                  is lq-rq, the variable part is null.

          A zone line has the form

               Zone  NAME        STDOFF  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
                lq.rq or lq..rq; a file name component is a maximal sub-
                string that does not contain lq/rq.

          STDOFF
                The amount of time to add to UT to get standard time,
                without any adjustment for daylight saving.  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.

     Page 6                       Plan 9             (printed 5/24/22)

     ZIC(8)                    (2020-08-13)                     ZIC(8)

          RULES The name of the rules that apply in the timezone or,
                alternatively, 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 stan-
                dard time and this amount matters.

          FORMAT
                The format for time zone abbreviations.  The pair of
                characters %s is used to show where the lqvariable
                partrq of the time zone abbreviation goes.  Alterna-
                tively, a format can use the pair of characters %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, min-
                utes, and seconds east (+) or west (-) of UT.  Alter-
                natively, a slash (/) separates standard and daylight
                abbreviations.  To conform to POSIX, a time zone
                abbreviation should contain only alphanumeric ASCII
                characters, lq+rq and lq-rq.

          UNTIL The time at which the UT offset or the rule(s) change
                for a location.  It takes the form of one to four
                fields YEAR [MONTH [DAY [TIME]]].  If this is speci-
                fied, the time zone information is generated from the
                given UT offset and rule change until the time speci-
                fied, 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 lqcontinuationrq line; this has
                the same form as a zone line except that the string
                lqZonerq and the name are omitted, as the continuation
                line will place information starting at the time spec-
                ified as the lquntilrq information in the previous line
                in the file used by the previous line.  Continuation
                lines may contain lquntilrq 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 oth-
          erwise take effect in the earlier zone or continuation line,
          the rule is ignored.  A zone or continuation line L with a
          named rule set starts with standard time by default: that
          is, any of L's timestamps preceding L's earliest rule use
          the rule in effect after L's first transition into standard
          time.  In a single zone it is an error if two rules take

     Page 7                       Plan 9             (printed 5/24/22)

     ZIC(8)                    (2020-08-13)                     ZIC(8)

          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 input.  However, the behavior is unspecified if mul-
          tiple zone or link lines define the same name, or if the
          source of one link line is the target of another.

          The file that describes leap seconds can have leap lines and
          an expiration line.  Leap lines 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 lq+rq if a second
          was added or lq-rq if a second was skipped.  The R/S field
          should be (an abbreviation of) lqStationaryrq if the leap sec-
          ond time given by the other fields should be interpreted as
          UTC or (an abbreviation of) lqRollingrq if the leap second
          time given by the other fields should be interpreted as
          local (wall clock) time.

          The expiration line, if present, has the form:

               Expires  YEAR  MONTH  DAY  HH:MM:SS

          For example:

               Expires  2020  Dec    28   00:00:00

          The YEAR, MONTH, DAY, and HH:MM:SS fields give the expira-
          tion timestamp in UTC for the leap second table; zic outputs
          this expiration timestamp by truncating the end of the out-
          put file to the timestamp.  If there is no expiration line,
          zic also accepts a comment lq#expires E ...rq where E is the

     Page 8                       Plan 9             (printed 5/24/22)

     ZIC(8)                    (2020-08-13)                     ZIC(8)

          expiration timestamp as a decimal integer count of seconds
          since the Epoch, not counting leap seconds.  However, the
          lq#expiresrq comment is an obsolescent feature, and the leap
          second file should use an expiration line instead of relying
          on a comment.

     EXTENDED EXAMPLE
          Here is an extended example of zic input, intended to illus-
          trate many of its features.  In this example, the EU rules
          are for the European Union and for its predecessor organiza-
          tion, 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           STDOFF      RULES  FORMAT  [UNTIL]
            Zone    Europe/Zurich  0:34:08     -      LMT     1853 Jul 16
                                   0:29:45.50  -      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 offset was changed to 7 degrees 26
          minutes 22.50 seconds, which works out to 0:29:45.50; zic
          treats this by rounding it to 0:29:46.  After 1894-06-01 at
          00:00 the UT offset became one hour and Swiss daylight sav-
          ing rules (defined with lines beginning with lqRule Swissrq)
          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 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, lqLMTrq and lqBMTrq were initially
          used, respectively.  Since Swiss rules and later EU rules

     Page 9                       Plan 9             (printed 5/24/22)

     ZIC(8)                    (2020-08-13)                     ZIC(8)

          were applied, the time zone abbreviation has been CET for
          standard time and CEST for daylight saving time.

     FILES
          /etc/localtime
               Default local timezone file.

          /usr/share/zoneinfo
               Default timezone information directory.

     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 ear-
          liest transition time's rule to ensure that the earliest
          transition time recorded in the compiled 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 local (wall clock) time.  To get sepa-
          rate transitions use multiple zone continuation lines speci-
          fying transition instants using universal time.

     SEE ALSO
          tzfile(5), zdump(8)

     COLOPHON
          This page is part of release 5.10 of the Linux man-pages
          project.  A description of the project, information about
          reporting bugs, and the latest version of this page, can be
          found at https://www.kernel.org/doc/man-pages/.

     Page 10                      Plan 9             (printed 5/24/22)