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       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 input.  If  a  filename  is  “-”,  standard
       input is read.


              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
              incompatibilities  in  older  software, such as software that mishandles 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
              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

                   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              This feature is obsolete and poorly supported.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, “zic -r @0” omits data
              intended  for  negative  timestamps  (i.e.,  before  the  Epoch),   and   “zic   -r
              @0/@2147483648” outputs data intended only for nonnegative timestamps that fit into
              31-bit signed integers.  On platforms with GNU date, “zic -r  @$(date  +%s)”  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 configuration link in the named  file
              rather than in the standard location.

       -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 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

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

              A timestamp contains fractional seconds.  Pre-2018 versions of zic do  not  support

              The  input  contains  abbreviations that are mishandled by pre-2018 versions of zic
              due to a longstanding coding bug.  These abbreviations include “L” for “Link”, “mi”
              for “min”, “Sa” for “Sat”, and “Su” for “Sun”.

              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  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 compatibility issues  affect  only  timestamps
              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, “-”, “/”, or  “_”;
              or  it  contains  a  file  name  component that contains more than 14 bytes or that
              starts with “-”.


       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) ⟨
       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 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.  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 “-” 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 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 abbreviation) 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  differing  time  value

       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

               A weekday name (e.g.,  Sunday)  or  a  weekday  name  preceded  by  “last”  (e.g.,
               lastSunday)  may  be  abbreviated  or spelled out in full.  There must be no white
               space characters within the ON field.  The “<=” and “>=” constructs can result  in
               a  day  in the neighboring month; for example, the IN-ON combination “Oct Sun>=31”
               stands for the first Sunday on or after October 31, even if that Sunday occurs  in

       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 “wall
               clock” 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 occurs at 00:59:60 local time, “1:00”
               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 standard 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.
               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        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  “.”
             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, 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.

       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 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  abbreviation  goes.   Alternatively,  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,  minutes,  and  seconds  east  (+) or west (−) of UT.
             Alternatively, a slash  (/)  separates  standard  and  daylight  abbreviations.   To
             conform  to  POSIX,  a time zone abbreviation should contain only alphanumeric ASCII
             characters, “+” and “-”.

       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 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.  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 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.

       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 “+” 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.

       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 expiration timestamp in UTC for the
       leap second table; zic outputs this expiration timestamp by  truncating  the  end  of  the
       output  file to the timestamp.  If there is no expiration line, zic also accepts a comment
       “#expires E ...” where E is the expiration timestamp as a decimal integer count of seconds
       since  the  Epoch,  not  counting  leap  seconds.   However,  the “#expires” comment is an
       obsolescent feature, and the leap second file should use an  expiration  line  instead  of
       relying on a comment.


       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           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°26′22.50″, 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 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 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  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 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 separate transitions use multiple zone continuation lines
       specifying transition instants using universal time.


       tzfile(5), zdump(8)


       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

                                            2020-08-13                                     ZIC(8)