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authorDaniel Baumann <daniel.baumann@progress-linux.org>2024-04-15 19:40:15 +0000
committerDaniel Baumann <daniel.baumann@progress-linux.org>2024-04-15 19:40:15 +0000
commit399644e47874bff147afb19c89228901ac39340e (patch)
tree1c4c0b733f4c16b5783b41bebb19194a9ef62ad1 /man8/zic.8
parentInitial commit. (diff)
downloadmanpages-399644e47874bff147afb19c89228901ac39340e.tar.xz
manpages-399644e47874bff147afb19c89228901ac39340e.zip
Adding upstream version 6.05.01.upstream/6.05.01
Signed-off-by: Daniel Baumann <daniel.baumann@progress-linux.org>
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+.\" This file is in the public domain, so clarified as of
+.\" 2009-05-17 by Arthur David Olson.
+.TH zic 8 "" "Time Zone Database"
+.SH NAME
+zic \- timezone compiler
+.SH SYNOPSIS
+.B zic
+[
+.I option
+\&... ] [
+.I filename
+\&... ]
+.SH DESCRIPTION
+.ie '\(lq'' .ds lq \&"\"
+.el .ds lq \(lq\"
+.ie '\(rq'' .ds rq \&"\"
+.el .ds rq \(rq\"
+.de q
+\\$3\*(lq\\$1\*(rq\\$2
+..
+.ie '\(la'' .ds < <
+.el .ds < \(la
+.ie '\(ra'' .ds > >
+.el .ds > \(ra
+.ie \n(.g \{\
+. ds : \:
+. ds - \f(CR-\fP
+.\}
+.el \{\
+. ds :
+. ds - \-
+.\}
+.ds d " degrees
+.ds m " minutes
+.ds s " seconds
+.ds _ " \&
+.if t \{\
+. if \n(.g .if c \(de .if c \(fm .if c \(sd \{\
+. ds d \(de
+. ds m \(fm
+. ds s \(sd
+. ds _ \|
+. \}
+.\}
+The
+.B zic
+program reads text from the file(s) named on the command line
+and creates the timezone information format (TZif) files
+specified in this input.
+If a
+.I filename
+is
+.q "\*-" ,
+standard input is read.
+.SH OPTIONS
+.TP
+.B "\*-\*-version"
+Output version information and exit.
+.TP
+.B \*-\*-help
+Output short usage message and exit.
+.TP
+.BI "\*-b " bloat
+Output backward-compatibility data as specified by
+.IR bloat .
+If
+.I bloat
+is
+.BR 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
+.I bloat
+is
+.BR slim ,
+keep the output files small; this can help check for the bugs
+and incompatibilities.
+The default is
+.BR slim ,
+as software that mishandles 64-bit data typically
+mishandles timestamps after the year 2038 anyway.
+Also see the
+.B \*-r
+option for another way to alter output size.
+.TP
+.BI "\*-d " directory
+Create time conversion information files in the named directory rather than
+in the standard directory named below.
+.TP
+.BI "\*-l " timezone
+Use
+.I timezone
+as local time.
+.B zic
+will act as if the input contained a link line of the form
+.sp
+.ti +.5i
+.ta \w'Link\0\0'u +\w'\fItimezone\fP\0\0'u
+Link \fItimezone\fP localtime
+.sp
+If
+.I timezone
+is
+.BR \*- ,
+any already-existing link is removed.
+.TP
+.BI "\*-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.
+.TP
+.BI "\*-p " timezone
+Use
+.IR timezone 's
+rules when handling nonstandard
+TZ strings like "EET\*-2EEST" that lack transition rules.
+.B zic
+will act as if the input contained a link line of the form
+.sp
+.ti +.5i
+Link \fItimezone\fP posixrules
+.sp
+Unless
+.I timezone is
+.q "\*-" ,
+this option 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 "\*-b slim"
+if
+.IR timezone 's
+transitions are at standard time or Universal Time (UT) instead of local time.
+.sp
+If
+.I timezone
+is
+.BR \*- ,
+any already-existing link is removed.
+.TP
+.BR "\*-r " "[\fB@\fP\fIlo\fP][\fB/@\fP\fIhi\fP]"
+Limit the applicability of output files
+to timestamps in the range from
+.I lo
+(inclusive) to
+.I hi
+(exclusive), where
+.I lo
+and
+.I hi
+are possibly signed decimal counts of seconds since the Epoch
+(1970-01-01 00:00:00 UTC).
+Omitted counts default to extreme values.
+The output files use UT offset 0 and abbreviation
+.q "\*-00"
+in place of the omitted timestamp data.
+For example,
+.q "zic \*-r @0"
+omits data intended for negative timestamps (i.e., before the Epoch), and
+.q "zic \*-r @0/@2147483648"
+outputs data intended only for nonnegative timestamps that fit into
+31-bit signed integers.
+On platforms with GNU
+.BR date ,
+.q "zic \*-r @$(date +%s)"
+omits data intended for past timestamps.
+Although this option typically reduces the output file's size,
+the size can increase due to the need to represent the timestamp range
+boundaries, particularly if
+.I hi
+causes a TZif file to contain explicit entries for
+.RI pre- hi
+transitions rather than concisely representing them
+with an extended POSIX TZ string.
+Also see the
+.B "\*-b slim"
+option for another way to shrink output size.
+.TP
+.BI "\*-R @" hi
+Generate redundant trailing explicit transitions for timestamps
+that occur less than
+.I hi
+seconds since the Epoch, even though the transitions could be
+more concisely represented via the extended POSIX TZ string.
+This option does not affect the represented timestamps.
+Although it accommodates nonstandard TZif readers
+that ignore the extended POSIX TZ string,
+it increases the size of the altered output files.
+.TP
+.BI "\*-t " file
+When creating local time information, put the configuration link in
+the named file rather than in the standard location.
+.TP
+.B \*-v
+Be more verbose, and complain about the following situations:
+.RS
+.PP
+The input specifies a link to a link,
+something not supported by some older parsers, including
+.B zic
+itself through release 2022e.
+.PP
+A year that appears in a data file is outside the range
+of representable years.
+.PP
+A time of 24:00 or more appears in the input.
+Pre-1998 versions of
+.B zic
+prohibit 24:00, and pre-2007 versions prohibit times greater than 24:00.
+.PP
+A rule goes past the start or end of the month.
+Pre-2004 versions of
+.B zic
+prohibit this.
+.PP
+A time zone abbreviation uses a
+.B %z
+format.
+Pre-2015 versions of
+.B zic
+do not support this.
+.PP
+A timestamp contains fractional seconds.
+Pre-2018 versions of
+.B zic
+do not support this.
+.PP
+The input contains abbreviations that are mishandled by pre-2018 versions of
+.B zic
+due to a longstanding coding bug.
+These abbreviations include
+.q L
+for
+.q Link ,
+.q mi
+for
+.q min ,
+.q Sa
+for
+.q Sat ,
+and
+.q Su
+for
+.q Sun .
+.PP
+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 2023 this problem
+occurs for Morocco's daylight-saving rules, as these rules are based
+on predictions for when Ramadan will be observed, something that
+an extended POSIX TZ string cannot represent.
+.PP
+The output contains data that may not be handled properly by client
+code designed for older
+.B zic
+output formats. These compatibility issues affect only timestamps
+before 1970 or after the start of 2038.
+.PP
+The output contains a truncated leap second table,
+which can cause some older TZif readers to misbehave.
+This can occur if the
+.B "\*-L"
+option is used, and either an Expires line is present or
+the
+.B "\*-r"
+option is also used.
+.PP
+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.
+.PP
+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.
+.PP
+An output file name contains a byte that is not an ASCII letter,
+.q "\*-" ,
+.q "/" ,
+or
+.q "_" ;
+or it contains a file name component that contains more than 14 bytes
+or that starts with
+.q "\*-" .
+.RE
+.SH FILES
+Input files use the format described in this section; output files use
+.BR tzfile (5)
+format.
+.PP
+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 2048 bytes counting the newline, 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)
+\*<https://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
+.B \*-v
+option.
+.PP
+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.
+.PP
+Names must be in English and are case insensitive.
+They appear in several contexts, and include month and weekday names
+and keywords such as
+.BR "maximum" ,
+.BR "only" ,
+.BR "Rolling" ,
+and
+.BR "Zone" .
+A name can be abbreviated by omitting all but an initial prefix; any
+abbreviation must be unambiguous in context.
+.PP
+A rule line has the form
+.nf
+.ti +.5i
+.ta \w'Rule\0\0'u +\w'NAME\0\0'u +\w'FROM\0\0'u +\w'1973\0\0'u +\w'\*-\0\0'u +\w'Apr\0\0'u +\w'lastSun\0\0'u +\w'2:00w\0\0'u +\w'1:00d\0\0'u
+.sp
+Rule NAME FROM TO \*- IN ON AT SAVE LETTER/S
+.sp
+For example:
+.ti +.5i
+.sp
+Rule US 1967 1973 \*- Apr lastSun 2:00w 1:00d D
+.sp
+.fi
+The fields that make up a rule line are:
+.TP "\w'LETTER/S'u"
+.B 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
+.q \*-
+nor
+.q + .
+To allow for future extensions,
+an unquoted name should not contain characters from the set
+.ie \n(.g .q \f(CR!$%&\(aq()*,/:;<=>?@[\e]\(ha\(ga{|}\(ti\fP .
+.el .ie t .q \f(CW!$%&'()*,/:;<=>?@[\e]^\(ga{|}~\fP .
+.el .q !$%&'()*,/:;<=>?@[\e]^`{|}~ .
+.TP
+.B 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
+.B minimum
+(or an abbreviation) means the indefinite past.
+The word
+.B 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 types.
+.TP
+.B TO
+Gives the final year in which the rule applies.
+In addition to
+.B minimum
+and
+.B maximum
+(as above),
+the word
+.B only
+(or an abbreviation)
+may be used to repeat the value of the
+.B FROM
+field.
+.TP
+.B \*-
+Is a reserved field and should always contain
+.q \*-
+for compatibility with older versions of
+.BR zic .
+It was previously known as the
+.B TYPE
+field, which could contain values to allow a
+separate script to further restrict in which
+.q types
+of years the rule would apply.
+.TP
+.B IN
+Names the month in which the rule takes effect.
+Month names may be abbreviated.
+.TP
+.B ON
+Gives the day on which the rule takes effect.
+Recognized forms include:
+.nf
+.in +.5i
+.sp
+.ta \w'Sun<=25\0\0'u
+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
+.fi
+.in -.5i
+.sp
+A weekday name (e.g.,
+.BR "Sunday" )
+or a weekday name preceded by
+.q "last"
+(e.g.,
+.BR "lastSunday" )
+may be abbreviated or spelled out in full.
+There must be no white space characters within the
+.B ON
+field.
+The
+.q <=
+and
+.q >=
+constructs can result in a day in the neighboring month;
+for example, the IN-ON combination
+.q "Oct Sun>=31"
+stands for the first Sunday on or after October 31,
+even if that Sunday occurs in November.
+.TP
+.B 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:
+.nf
+.in +.5i
+.sp
+.ta \w'00:19:32.13\0\0'u
+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
+.fi
+.in -.5i
+.sp
+Although
+.B 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
+.B w
+if the given time is local or
+.q "wall clock"
+time,
+.B s
+if the given time is standard time without any adjustment for daylight saving,
+or
+.B u
+(or
+.B g
+or
+.BR 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,
+.q "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
+.B AT
+field would show the specified date and time of day.
+.TP
+.B 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
+.B AT
+field
+except with a different set of suffix letters:
+.B s
+for standard time and
+.B d
+for daylight saving time.
+The suffix letter is typically omitted, and defaults to
+.B s
+if the offset is zero and to
+.B 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,
+.B zic
+does not distinguish a 10:30 standard time plus an 0:30
+.B SAVE
+from a 10:00 standard time plus a 1:00
+.BR SAVE .
+.TP
+.B LETTER/S
+Gives the
+.q "variable part"
+(for example, the
+.q "S"
+or
+.q "D"
+in
+.q "EST"
+or
+.q "EDT" )
+of time zone abbreviations to be used when this rule is in effect.
+If this field is
+.q \*- ,
+the variable part is null.
+.PP
+A zone line has the form
+.sp
+.nf
+.ti +.5i
+.ta \w'Zone\0\0'u +\w'Asia/Amman\0\0'u +\w'STDOFF\0\0'u +\w'Jordan\0\0'u +\w'FORMAT\0\0'u
+Zone NAME STDOFF RULES FORMAT [UNTIL]
+.sp
+For example:
+.sp
+.ti +.5i
+Zone Asia/Amman 2:00 Jordan EE%sT 2017 Oct 27 01:00
+.sp
+.fi
+The fields that make up a zone line are:
+.TP "\w'STDOFF'u"
+.B 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
+.q ".\&"
+or
+.q ".." ;
+a file name component is a maximal substring that does not contain
+.q "/" .
+.TP
+.B 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
+.B AT
+and
+.B SAVE
+fields of rule lines, except without suffix letters;
+begin the field with a minus sign if time must be subtracted from UT.
+.TP
+.B 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 the amount of time to be added to local standard time
+and whether the resulting time is standard or daylight saving.
+If this field is
+.B \*-
+then standard time always applies.
+When an amount of time is given, only the sum of standard time and
+this amount matters.
+.TP
+.B FORMAT
+The format for time zone abbreviations.
+The pair of characters
+.B %s
+is used to show where the
+.q "variable part"
+of the time zone abbreviation goes.
+Alternatively, a format can use the pair of characters
+.B %z
+to stand for the UT offset in the form
+.RI \(+- hh ,
+.RI \(+- hhmm ,
+or
+.RI \(+- hhmmss ,
+using the shortest form that does not lose information, where
+.IR hh ,
+.IR mm ,
+and
+.I 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,
+.q "+"
+and
+.q "\*-".
+By convention, the time zone abbreviation
+.q "\*-00"
+is a placeholder that means local time is unspecified.
+.TP
+.B 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.
+.IP
+The next line must be a
+.q "continuation"
+line; this has the same form as a zone line except that the
+string
+.q "Zone"
+and the name are omitted, as the continuation line will
+place information starting at the time specified as the
+.q "until"
+information in the previous line in the file used by the previous line.
+Continuation lines may contain
+.q "until"
+information, just as zone lines do, indicating that the next line is a further
+continuation.
+.PP
+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
+.I L
+with a named rule set starts with standard time by default:
+that is, any of
+.IR L 's
+timestamps preceding
+.IR L 's
+earliest rule use the rule in effect after
+.IR 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.
+.PP
+If a continuation line subtracts
+.I N
+seconds from the UT offset after a transition that would be
+interpreted to be later if using the continuation line's UT offset and
+rules, the
+.q "until"
+time of the previous zone or continuation line is interpreted
+according to the continuation line's UT offset and rules, and any rule
+that would otherwise take effect in the next
+.I N
+seconds is instead assumed to take effect simultaneously.
+For example:
+.br
+.ne 7
+.nf
+.in +2m
+.ta \w'# Rule\0\0'u +\w'NAME\0\0'u +\w'FROM\0\0'u +\w'2006\0\0'u +\w'\*-\0\0'u +\w'Oct\0\0'u +\w'lastSun\0\0'u +\w'2:00\0\0'u +\w'SAVE\0\0'u
+.sp
+# Rule NAME FROM TO \*- IN ON AT SAVE LETTER/S
+Rule US 1967 2006 - Oct lastSun 2:00 0 S
+Rule US 1967 1973 - Apr lastSun 2:00 1:00 D
+.ta \w'Zone\0\0America/Menominee\0\0'u +\w'STDOFF\0\0'u +\w'RULES\0\0'u +\w'FORMAT\0\0'u
+# Zone\0\0NAME STDOFF RULES FORMAT [UNTIL]
+Zone\0\0America/Menominee \*-5:00 \*- EST 1973 Apr 29 2:00
+ \*-6:00 US C%sT
+.sp
+.in
+.fi
+Here, an incorrect reading would be there were two clock changes on 1973-04-29,
+the first from 02:00 EST (\*-05) to 01:00 CST (\*-06),
+and the second an hour later from 02:00 CST (\*-06) to 03:00 CDT (\*-05).
+However,
+.B zic
+interprets this more sensibly as a single transition from 02:00 CST (\*-05) to
+02:00 CDT (\*-05).
+.PP
+A link line has the form
+.sp
+.nf
+.ti +.5i
+.ta \w'Link\0\0'u +\w'Europe/Istanbul\0\0'u
+Link TARGET LINK-NAME
+.sp
+For example:
+.sp
+.ti +.5i
+Link Europe/Istanbul Asia/Istanbul
+.sp
+.fi
+The
+.B TARGET
+field should appear as the
+.B NAME
+field in some zone line or as the
+.B LINK-NAME
+field in some link line.
+The
+.B LINK-NAME
+field is used as an alternative name for that zone;
+it has the same syntax as a zone line's
+.B NAME
+field.
+Links can chain together, although the behavior is unspecified if a
+chain of one or more links does not terminate in a Zone name.
+A link line can appear before the line that defines the link target.
+For example:
+.sp
+.ne 3
+.nf
+.in +2m
+.ta \w'Zone\0\0'u +\w'Greenwich\0\0'u
+Link Greenwich G_M_T
+Link Etc/GMT Greenwich
+Zone Etc/GMT\0\00\0\0\*-\0\0GMT
+.sp
+.in
+.fi
+The two links are chained together, and G_M_T, Greenwich, and Etc/GMT
+all name the same zone.
+.PP
+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.
+.PP
+The file that describes leap seconds can have leap lines and an
+expiration line.
+Leap lines have the following form:
+.nf
+.ti +.5i
+.ta \w'Leap\0\0'u +\w'YEAR\0\0'u +\w'MONTH\0\0'u +\w'DAY\0\0'u +\w'HH:MM:SS\0\0'u +\w'CORR\0\0'u
+.sp
+Leap YEAR MONTH DAY HH:MM:SS CORR R/S
+.sp
+For example:
+.ti +.5i
+.sp
+Leap 2016 Dec 31 23:59:60 + S
+.sp
+.fi
+The
+.BR YEAR ,
+.BR MONTH ,
+.BR DAY ,
+and
+.B HH:MM:SS
+fields tell when the leap second happened.
+The
+.B CORR
+field
+should be
+.q "+"
+if a second was added
+or
+.q "\*-"
+if a second was skipped.
+The
+.B R/S
+field
+should be (an abbreviation of)
+.q "Stationary"
+if the leap second time given by the other fields should be interpreted as UTC
+or
+(an abbreviation of)
+.q "Rolling"
+if the leap second time given by the other fields should be interpreted as
+local (wall clock) time.
+.PP
+Rolling leap seconds were implemented back when it was not
+clear whether common practice was rolling or stationary,
+with concerns that one would see
+Times Square ball drops where there'd be a
+.q "3... 2... 1... leap... Happy New Year"
+countdown, placing the leap second at
+midnight New York time rather than midnight UTC.
+However, this countdown style does not seem to have caught on,
+which means rolling leap seconds are not used in practice;
+also, they are not supported if the
+.B \*-r
+option is used.
+.PP
+The expiration line, if present, has the form:
+.nf
+.ti +.5i
+.ta \w'Expires\0\0'u +\w'YEAR\0\0'u +\w'MONTH\0\0'u +\w'DAY\0\0'u
+.sp
+Expires YEAR MONTH DAY HH:MM:SS
+.sp
+For example:
+.ti +.5i
+.sp
+Expires 2020 Dec 28 00:00:00
+.sp
+.fi
+The
+.BR YEAR ,
+.BR MONTH ,
+.BR DAY ,
+and
+.B HH:MM:SS
+fields give the expiration timestamp in UTC for the leap second table.
+.br
+.ne 22
+.SH "EXTENDED EXAMPLE"
+Here is an extended example of
+.B zic
+input, intended to illustrate many of its features.
+.nf
+.in +2m
+.ta \w'# Rule\0\0'u +\w'NAME\0\0'u +\w'FROM\0\0'u +\w'1973\0\0'u +\w'\*-\0\0'u +\w'Apr\0\0'u +\w'lastSun\0\0'u +\w'2:00\0\0'u +\w'SAVE\0\0'u
+.sp
+# Rule NAME FROM TO \*- 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 \*-
+.sp .5
+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 \*-
+.sp
+.ta \w'# Zone\0\0'u +\w'Europe/Zurich\0\0'u +\w'0:29:45.50\0\0'u +\w'RULES\0\0'u +\w'FORMAT\0\0'u
+# 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
+.sp
+Link Europe/Zurich Europe/Vaduz
+.sp
+.in
+.fi
+In this example, the EU rules are for the European Union
+and for its predecessor organization, the European Communities.
+The timezone is named Europe/Zurich and it has the alias 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\*d\*_26\*m\*_22.50\*s,
+which works out to 0:29:45.50;
+.B 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
+.q "Rule Swiss")
+apply. From 1981 to the present, EU daylight saving rules have
+applied, and the UTC offset has remained at one hour.
+.PP
+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.
+.PP
+For purposes of display,
+.q "LMT"
+and
+.q "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.
+.SH FILES
+.TP
+.I /etc/localtime
+Default local timezone file.
+.TP
+.I /usr/share/zoneinfo
+Default timezone information directory.
+.SH NOTES
+For areas with more than two types of local time,
+you may need to use local standard time in the
+.B AT
+field of the earliest transition time's rule to ensure that
+the earliest transition time recorded in the compiled file is correct.
+.PP
+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,
+.B 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.
+.SH SEE ALSO
+.BR tzfile (5),
+.BR zdump (8)