.\" This page is in the public domain
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.\"
-.TH ZIC 8 2019-03-06 "" "Linux System Administration"
+.TH ZIC 8 2020-04-27 "" "Linux System Administration"
.SH NAME
zic \- timezone compiler
.SH SYNOPSIS
.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.
+Although the default is currently
+.BR fat ,
+this is intended to change in future
+.B zic
+versions, as software that mishandles the 64-bit data typically
+mishandles timestamps after the year 2038 anyway.
+Also see the
+.B \*-r
+option for another way to shrink output size.
+.TP
.BI "\*-d " directory
Create time conversion information files in the named directory rather than
in the standard directory named below.
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
.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 POSIX-format
-timezone environment variables.
+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
+This feature is obsolete and poorly supported.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 "\*-b slim"
+if
+.IR timezone 's
+transitions are at standard time or Universal Time (UT) instead of local time.
.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.
+.BR "\*-r " "[\fB@\fP\fIlo\fP][\fB/@\fP\fIhi\fP]"
+Reduce the size of output files by limiting their applicability
+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.
+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.
+Also see the
+.B "\*-b slim"
+option for another way to shrink output size.
+.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:
The input specifies a link to a link.
.PP
A year that appears in a data file is outside the range
-of years representable by
-.BR time (2)
-values.
+of representable years.
.PP
A time of 24:00 or more appears in the input.
Pre-1998 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 2013 this problem
+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.
output formats. These compatibility issues affect only timestamps
before 1970 or after the start of 2038.
.PP
-A time zone abbreviation has fewer than 3 characters.
-POSIX requires at least 3.
+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 "\*-" ,
or that starts with
.q "\*-" .
.RE
-.TP
-.B \*-s
-Limit time values stored in output files to values that are the same
-whether they're taken to be signed or unsigned.
-You can use this option to generate SVVS-compatible files.
+.SH FILES
+Input files use the format described in this section; output files use
+.IR 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
For example:
.ti +.5i
.sp
-Rule US 1967 1973 \*- Apr lastSun 2:00w 1:00 D
+Rule US 1967 1973 \*- Apr lastSun 2:00w 1:00d D
.sp
.fi
The fields that make up a rule line are:
(e.g.,
.BR "lastSunday" )
may be abbreviated or spelled out in full.
-Note that there must be no spaces within the
+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.
+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
2 time in hours
2:00 time in hours and minutes
01:28:14 time in hours, minutes, and seconds
-15:00 24-hour format time (for times after noon)
+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
-where hour 0 is midnight at the start of the day,
-and hour 24 is midnight at the end of the day.
+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
+if the given time is local or
.q "wall clock"
time,
.B s
-if the given time is local
-.q "standard"
-time, or
+if the given time is standard time without any adjustment for daylight saving,
+or
.B u
(or
.B g
.BR z )
if the given time is universal time;
in the absence of an indicator,
-wall clock time is assumed.
+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
.TP
.B SAVE
Gives the amount of time to be added to local standard time when the rule is in
-effect.
+effect, and whether the resulting time is standard or daylight saving.
This field has the same format as the
.B AT
field
-(although, of course, the
-.B w
-and
+except with a different set of suffix letters:
.B s
-suffixes are not used).
+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.
.sp
.nf
.ti +.5i
-.ta \w'Zone\0\0'u +\w'Asia/Amman\0\0'u +\w'UTOFF\0\0'u +\w'Jordan\0\0'u +\w'FORMAT\0\0'u
-Zone NAME UTOFF RULES FORMAT [UNTIL]
+.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
.sp
.fi
The fields that make up a zone line are:
-.TP "\w'UTOFF'u"
+.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
a file name component is a maximal substring that does not contain
.q "/" .
.TP
-.B UTOFF
-The amount of time to add to UT to get standard time.
+.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
.TP
.B UNTIL
The time at which the UT offset or the rule(s) change for a location.
-It takes the form of YEAR [MONTH [DAY [TIME]]].
+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
.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
define the same name, or if the source of one link line is the target
of another.
.PP
-Lines in the file that describes leap seconds have the following form:
+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
(an abbreviation of)
.q "Rolling"
if the leap second time given by the other fields should be interpreted as
-local wall clock time.
+local (wall clock) time.
+.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;
+.B zic
+outputs this expiration timestamp by truncating the end of the output
+file to the timestamp.
+If there is no expiration line,
+.B zic
+also accepts a comment
+.q "#expires \fIE\fP ...\&"
+where
+.I E
+is the expiration timestamp as a decimal integer count of seconds
+since the Epoch, not counting leap seconds.
+However, the
+.q "#expires"
+comment is an obsolescent feature,
+and the leap second file should use an expiration line
+instead of relying on a comment.
.SH "EXTENDED EXAMPLE"
Here is an extended example of
.B zic
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'0:34:08\0\0'u +\w'RULES\0\0'u +\w'FORMAT\0\0'u
-# Zone NAME UTOFF RULES FORMAT [UNTIL]
+.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
- 0:29:46 \*- BMT 1894 Jun
+ 0:29:45.50 \*- BMT 1894 Jun
1:00 Swiss CE%sT 1981
1:00 EU CE%sT
.sp
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\(de\|26\(fm\|22.50\(sd; although this works out to
-0:29:45.50, the input format cannot represent fractional seconds so it
-is rounded here. After 1894-06-01 at 00:00 the UT offset became one hour
+was changed to
+.ds o 7 degrees 26 minutes 22.50 seconds
+.if \n(.g .if c \(de .if c \(fm .if c \(sd .ds o 7\(de\|26\(fm\|22.50\(sd
+\*o,
+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
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 wall clock time).
+without any change in local (wall clock) time.
To get separate transitions
use multiple zone continuation lines
specifying transition instants using universal time.
projects / thirdparty / man-pages.git / commitdiff
