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

NAME
     zic -- timezone compiler

SYNOPSIS
     zic [--version] [--help] [-b] [-d directory] [-L leapsecondfilename]
         [-l localtime] [-p posixrules] [-s] [-t file] [-v] [-y command]
         [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 -, standard 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 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 any-
                 way.  Also see the -r option for another way to shrink output
                 size.
     -d directory
                 Create time conversion information files in the named direc-
                 tory rather than in the standard directory named below.
     -l timezone
                 Use the 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 POSIX-format TZ strings
                 like "EET2EEST" 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                 This feature is obsolete and poorly supported.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 UT instead of
                 local time.
     -r [@lo / [@hi]]
                 Reduce the size of output files by limiting their applicabil-
                 ity 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.  Or using date(1),

                 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 this.

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

                 -   A timestamp contains fractional seconds.  Pre-2018 ver-
                     sions 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 "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 can-
                     not be represented.

                 -   The output contains data that may not be handled properly
                     by client code designed for older zic(8) 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 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 typi-
     cally 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 another
     by one or more white space characters.  The white space characters are
     space, form feed, carriage return, newline, tab, and vertical tab.  Lead-
     ing 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 charac-
     ters 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
     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 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
               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.  A weekday name (e.g., "Sunday") or a weekday name pre-
               ceded 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 com-
               bination "Oct Sun>=31" tands 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 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,
               "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 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.

     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           STDOFF    RULES/SAVE     FORMAT    [UNTIL]

     For example:

           Zone Asia/Amman     2:00 Jordan    EE%sT     2017 Oct 27 1:00

     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
                 "/".

     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.

     RULES       The name of the rules that apply in the timezone or, alterna-
                 tively, a field in the same format as a rule-line SAVE col-
                 umn, giving of the amount of time to be added to local stan-
                 dard 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.

     FORMAT      The format for time zone abbreviations.  The pair of charac-
                 ters %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.  Alterna-
                 tively, a slash (/) separates standard and daylight abbrevia-
                 tions.  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 pre-
                 vious line.  Continuation lines may contain until informa-
                 tion, 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 with a named rule set starts with standard time
     by default: that is, any of timestamps preceding earliest rule use the
     rule in effect after 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 field.

     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 tar-
     get 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 hap-
     pened.  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.  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/SAVE 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 sec-
     onds east of UT until 1853-07-16 at 00:00, when the legal offset was
     changed to 726'22.50''; which this 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 From 1981 to the present, EU daylight saving rules have

     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 complete-
     ness.  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.

FILES
     Input files use the format described in this section; output files use
     tzfile(5) format.
     /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 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 sav-
     ing at the new UT offset without any change in local (wall clock) time.
     To get separate transitions use multiple zone continuation lines specify-
     ing transition instants using universal time.

SEE ALSO
     tzfile(5), zdump(8)

NetBSD 9.0                       July 2, 2019                       NetBSD 9.0

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©1994 Man-cgi 1.15, Panagiotis Christias
©1996-2019 Modified for NetBSD by Kimmo Suominen