.de q
\\$3\*(lq\\$1\*(rq\\$2
..
-.ie \n(.g .ds - \f(CR-\fP
-.el .ds - \-
The timezone information files used by
.BR tzset (3)
are typically found under a directory with a name like
.IR /usr/share/zoneinfo .
-These files use the format described in Internet RFC 8536.
+These files use the format described in Internet RFC 9636.
Each file is a sequence of 8-bit bytes.
In a file, a binary integer is represented by a sequence of one or
more bytes in network order (bigendian, or high-order byte first),
and a boolean is represented by a one-byte binary integer that is
either 0 (false) or 1 (true).
The format begins with a 44-byte header containing the following fields:
-.RS 2
-.IP \(bu 3
+.RS "\w' 'u"
+.IP \(bu "\w'\(bu 'u"
The magic four-byte ASCII sequence
.q "TZif"
identifies the file as a timezone information file.
Fifteen bytes containing zeros reserved for future use.
.IP \(bu
Six four-byte integer values, in the following order:
-.RS
-.TP 2
+.RS "\w'\(bu 'u"
+.TP "\w' 'u"
.B tzh_ttisutcnt
The number of UT/local indicators stored in the file.
(UT is Universal Time.)
.PP
The above header is followed by the following fields, whose lengths
depend on the contents of the header:
-.RS 2
-.IP \(bu 3
+.RS "\w' 'u"
+.IP \(bu "\w'\(bu 'u"
.B tzh_timecnt
four-byte signed integer values sorted in ascending order.
These values are written in network byte order.
starting with the same-indexed transition time
and continuing up to but not including the next transition time.
(The last time type is present only for consistency checking with the
-POSIX.1-2017-style TZ string described below.)
+proleptic TZ string described below.)
These values serve as indices into the next field.
.IP \(bu
.B tzh_typecnt
serves as an index into the array of time zone abbreviation bytes
that follow the
.B ttinfo
-entries in the file; if the designated string is "\*-00", the
+entries in the file; if the designated string is "\-00", the
.B ttinfo
entry is a placeholder indicating that local time is unspecified.
The
.IP \(bu
.B tzh_leapcnt
pairs of four-byte values, written in network byte order;
-the first value of each pair gives the nonnegative time
+the first value of each pair gives the non-negative time
(as returned by
.BR time (2))
at which a leap second occurs or at which the leap second table expires;
except that if the last pair has the same correction as the previous one,
the last pair denotes the leap second table's expiration time.
Each leap second is at the end of a UTC calendar month.
-The first leap second has a nonnegative occurrence time,
+The first leap second has a non-negative occurrence time,
and is a positive leap second if and only if its correction is positive;
the correction for each leap second after the first differs
from the previous leap second by either 1 for a positive leap second,
The standard/wall and UT/local indicators were designed for
transforming a TZif file's transition times into transitions appropriate
for another time zone specified via
-a POSIX.1-2017-style TZ string that lacks rules.
-For example, when TZ="EET\*-2EEST" and there is no TZif file "EET\*-2EEST",
+a proleptic TZ string that lacks rules.
+For example, when TZ="EET\-2EEST" and there is no TZif file "EET\-2EEST",
the idea was to adapt the transition times from a TZif file with the
well-known name "posixrules" that is present only for this purpose and
is a copy of the file "Europe/Brussels", a file with a different UT offset.
-POSIX does not specify this obsolete transformational behavior,
+POSIX does not specify the details of this obsolete transformational behavior,
the default rules are installation-dependent, and no implementation
is known to support this feature for timestamps past 2037,
so users desiring (say) Greek time should instead specify
TZ="Europe/Athens" for better historical coverage, falling back on
-TZ="EET\*-2EEST,M3.5.0/3,M10.5.0/4" if POSIX conformance is required
+TZ="EET\-2EEST,M3.5.0/3,M10.5.0/4" if POSIX conformance is required
and older timestamps need not be handled accurately.
.PP
The
eight bytes are used for each transition time or leap second time.
(Leap second counts remain four bytes.)
After the second header and data comes a newline-enclosed string
-in the style of the contents of a POSIX.1-2017 TZ environment variable,
+in the style of the contents of a proleptic TZ,
for use in handling instants
after the last transition time stored in the file
or for all instants if the file has no transitions.
The TZ string is empty (i.e., nothing between the newlines)
-if there is no POSIX.1-2017-style representation for such instants.
-If nonempty, the TZ string must agree with the local time
+if there is no proleptic representation for such instants.
+If non-empty, the TZ string must agree with the local time
type after the last transition time if present in the eight-byte data;
for example, given the string
.q "WET0WEST,M3.5.0/1,M10.5.0"
with the time period from the indefinite past up to but not including
the earliest transition time.
.SS Version 3 format
-For version-3-format timezone files, the TZ string may
-use two minor extensions to the POSIX.1-2017 TZ format, as described in
-.BR newtzset (3).
-First, the hours part of its transition times may be signed and range from
-\-167 through 167 instead of the POSIX-required unsigned values
+For version-3-format timezone files, a TZ string (see
+.BR newtzset (3))
+may use the following POSIX.1-2024 extensions to POSIX.1-2017:
+First, as in TZ="<\-02>2<\-01>,M3.5.0/\-1,M10.5.0/0",
+the hours part of its transition times may be signed and range from
+\-167 through 167 instead of being limited to unsigned values
from 0 through 24.
-Second, DST is in effect all year if it starts
+Second, as in TZ="XXX3EDT4,0/0,J365/23", DST is in effect all year if it starts
January 1 at 00:00 and ends December 31 at 24:00 plus the difference
between daylight saving and standard time.
.SS Version 4 format
Time zone designations should consist of at least three (3)
and no more than six (6) ASCII characters from the set of
alphanumerics,
-.q "\*-",
+.q "\-",
and
.q "+".
This is for compatibility with POSIX requirements for
This section documents common problems in reading or writing TZif files.
Most of these are problems in generating TZif files for use by
older readers.
-The goals of this section are:
-.RS 2
-.IP \(bu 3
-to help TZif writers output files that avoid common
+The goals of this section are to help:
+.RS "\w' 'u"
+.IP \(bu "\w'\(bu 'u"
+TZif writers output files that avoid common
pitfalls in older or buggy TZif readers,
.IP \(bu
-to help TZif readers avoid common pitfalls when reading
+TZif readers avoid common pitfalls when reading
files generated by future TZif writers, and
.IP \(bu
-to help any future specification authors see what sort of
+any future specification authors see what sort of
problems arise when the TZif format is changed.
.RE
.PP
When complete compatibility was not achieved, an attempt was
made to limit glitches to rarely used timestamps and allow
simple partial workarounds in writers designed to generate
-new-version data useful even for older-version readers.
+newer-version data useful even for older-version readers.
This section attempts to document these compatibility issues and
-workarounds, as well as to document other common bugs in
+workarounds as well as documenting other common bugs in
readers.
.PP
Interoperability problems with TZif include the following:
-.RS 2
-.IP \(bu 3
+.RS "\w' 'u"
+.IP \(bu "\w'\(bu 'u"
Some readers examine only version 1 data.
As a partial workaround, a writer can output as much version 1
data as possible.
.IP \(bu
Some readers designed for version 2 might mishandle
timestamps after a version 3 or higher file's last transition, because
-they cannot parse extensions to POSIX.1-2017 in the TZ-like string.
+they cannot parse the POSIX.1-2024 extensions to POSIX.1-2017
+in the proleptic TZ string.
As a partial workaround, a writer can output more transitions
than necessary, so that only far-future timestamps are
mishandled by version 2 readers.
for a time zone with a never-used standard time (XXX, \-03)
and negative daylight saving time (EDT, \-04) all year.
Alternatively,
-as a partial workaround a writer can substitute standard time
+as a partial workaround, a writer can substitute standard time
for the next time zone east \(en e.g.,
.q "AST4"
for permanent
Atlantic Standard Time (\-04).
.IP \(bu
-Some readers designed for version 2 or 3, and that require strict
-conformance to RFC 8536, reject version 4 files whose leap second
-tables are truncated at the start or that end in expiration times.
+Some readers designed for version 2 or 3 and that require strict
+conformance to RFC 9636 reject version 4 files whose leap second
+tables are truncated at the start or end in expiration times.
.IP \(bu
Some readers ignore the footer, and instead predict future
timestamps from the time type of the last transition.
As a partial workaround, a writer can output more transitions
than necessary.
.IP \(bu
+Some stripped-down readers ignore everything but the footer,
+and use its proleptic TZ string to calculate all timestamps.
+Although this approach often works for current and future timestamps,
+it obviously has problems with past timestamps,
+and even for current timestamps it can fail for settings like
+TZ="Africa/Casablanca". This corresponds to a TZif file
+containing explicit transitions through the year 2087,
+followed by a footer containing the TZ string
+.q <+01>\-1 ,
+which should be used only for timestamps after the last
+explicit transition.
+.IP \(bu
Some readers do not use time type 0 for timestamps before
the first transition, in that they infer a time type using a
heuristic that does not always select time type 0.
first transition at an early time.
.IP \(bu
Some readers mishandle timestamps before the first
-transition that has a timestamp not less than \-2**31.
+transition that has a timestamp that is not less than \-2**31.
Readers that support only 32-bit timestamps are likely to be
more prone to this problem, for example, when they process
64-bit transitions only some of which are representable in 32
the minimum possible signed 64-bit value.
Timestamps less than \-2**59 are not recommended.
.IP \(bu
-Some readers mishandle TZ strings that
+Some readers mishandle proleptic TZ strings that
contain
.q "<"
or
These characters are not recommended.
.IP \(bu
Some readers may mishandle time zone abbreviations that
-contain fewer than 3 or more than 6 characters, or that
+contain fewer than 3 or more than 6 characters or that
contain ASCII characters other than alphanumerics,
-.q "\*-",
+.q "\-",
and
.q "+".
These abbreviations are not recommended.
offsets for the corresponding standard time.
These readers do not support locations like Ireland, which
uses the equivalent of the TZ string
-.q "IST\*-1GMT0,M10.5.0,M3.5.0/1",
+.q "IST\-1GMT0,M10.5.0,M3.5.0/1",
observing standard time
(IST, +01) in summer and daylight saving time (GMT, +00) in winter.
As a partial workaround, a writer can output data for the
.IP \(bu
Some readers generate ambiguous timestamps for positive leap seconds
that occur when the UTC offset is not a multiple of 60 seconds.
-For example, in a timezone with UTC offset +01:23:45 and with
+For example, with UTC offset +01:23:45 and
a positive leap second 78796801 (1972-06-30 23:59:60 UTC), some readers will
map both 78796800 and 78796801 to 01:23:45 local time the next day
instead of mapping the latter to 01:23:46, and they will map 78796815 to
.PP
Some interoperability problems are reader bugs that
are listed here mostly as warnings to developers of readers.
-.RS 2
-.IP \(bu 3
+.RS "\w' 'u"
+.IP \(bu "\w'\(bu 'u"
Some readers do not support negative timestamps.
Developers of distributed applications should keep this
in mind if they need to deal with pre-1970 data.
.IP \(bu
Some readers mishandle timestamps before the first
-transition that has a nonnegative timestamp.
+transition that has a non-negative timestamp.
Readers that do not support negative timestamps are likely to
be more prone to this problem.
.IP \(bu
Some readers mishandle time zone abbreviations like
-.q "\*-08"
+.q "\-08"
that contain
.q "+",
-.q "\*-",
+.q "\-",
or digits.
.IP \(bu
Some readers mishandle UT offsets that are out of the
range.
.IP \(bu
Some readers mishandle UT offsets in the range [\-3599, \-1]
-seconds from UT, because they integer-divide the offset by
+seconds from UT because they integer-divide the offset by
3600 to get 0 and then display the hour part as
.q "+00".
.IP \(bu
.BR zic (8).
.PP
Olson A, Eggert P, Murchison K. The Time Zone Information Format (TZif).
-2019 Feb.
-.UR https://\:datatracker.ietf.org/\:doc/\:html/\:rfc8536
-Internet RFC 8536
+October 2024.
+.UR https://\:www.rfc-editor.org/\:rfc/\:rfc9636
+Internet RFC 9636
.UE
-.UR https://\:doi.org/\:10.17487/\:RFC8536
-doi:10.17487/RFC8536
+.UR https://\:doi.org/\:10.17487/\:RFC9636
+doi:10.17487/RFC9636
.UE .
.SH NAME
tzselect \- select a timezone
.SH SYNOPSIS
-.ie \n(.g .ds - \f(CR-\fP
-.el .ds - \-
.ds d " degrees
.ds m " minutes
.ds s " seconds
.\}
.B tzselect
[
-.B \*-c
+.B \-c
.I coord
] [
-.B \*-n
+.B \-n
.I limit
] [
-.B \*-\*-help
+.B \-\-help
] [
-.B \*-\*-version
+.B \-\-version
]
.SH DESCRIPTION
The
All interaction with the user is done via standard input and standard error.
.SH OPTIONS
.TP
-.BI "\*-c " coord
+.BI "\-c " coord
Instead of asking for continent and then country and then city,
ask for selection from time zones whose largest cities
are closest to the location with geographical coordinates
.I SS
is present) seconds. The decimal point is that of the current locale.
For example, in the (default) C locale,
-.B "\*-c\ +40.689\*-074.045"
+.B "\-c\ +40.689\-074.045"
specifies 40.689\*d\*_N, 74.045\*d\*_W,
-.B "\*-c\ +4041.4\*-07402.7"
+.B "\-c\ +4041.4\-07402.7"
specifies 40\*d\*_41.4\*m\*_N, 74\*d\*_2.7\*m\*_W, and
-.B "\*-c\ +404121\*-0740240"
+.B "\-c\ +404121\-0740240"
specifies 40\*d\*_41\*m\*_21\*s\*_N, 74\*d\*_2\*m\*_40\*s\*_W.
If
.I coord
is not one of the documented forms, the resulting behavior is unspecified.
.TP
-.BI "\*-n " limit
+.BI "\-n " limit
When
-.B \*-c
+.B \-c
is used, display the closest
.I limit
locations (default 10).
.TP
-.B "\*-\*-help"
+.B "\-\-help"
Output help information and exit.
.TP
-.B "\*-\*-version"
+.B "\-\-version"
Output version information and exit.
.SH "ENVIRONMENT VARIABLES"
.TP
.de q
\\$3\*(lq\\$1\*(rq\\$2
..
-.ie \n(.g .ds - \f(CR-\fP
-.el .ds - \-
The
.B zdump
program prints the current time in each
.I timezone
named on the command line.
+A
+.I timezone
+of
+.B \-
+is treated as if it were /dev/stdin;
+this can be used to pipe TZif data into
+.BR zdump .
.SH OPTIONS
.TP
-.B \*-\*-version
+.B \-\-version
Output version information and exit.
.TP
-.B \*-\*-help
+.B \-\-help
Output short usage message and exit.
.TP
-.B \*-i
+.B \-i
Output a description of time intervals. For each
.I timezone
on the command line, output an interval-format description of the
.q "INTERVAL FORMAT"
below.
.TP
-.B \*-v
+.B \-v
Output a verbose description of time intervals.
For each
.I timezone
.I N
seconds east of Greenwich.
.TP
-.B \*-V
+.B \-V
Like
-.BR \*-v ,
+.BR \-v ,
except omit output concerning extreme time and year values.
This generates output that is easier to compare to that of
implementations with different time representations.
.TP
-.BI "\*-c " \fR[\fIloyear , \fR]\fIhiyear
+.BI "\-c " \fR[\fIloyear , \fR]\fIhiyear
Cut off interval output at the given year(s).
Cutoff times are computed using the proleptic Gregorian calendar with year 0
and with Universal Time (UT) ignoring leap seconds.
Cutoffs are at the start of each year, where the lower-bound
timestamp is inclusive and the upper is exclusive; for example,
-.B "\*-c 1970,2070"
+.B "\-c 1970,2070"
selects transitions on or after 1970-01-01 00:00:00 UTC
and before 2070-01-01 00:00:00 UTC.
The default cutoff is
-.BR \*-500,2500 .
+.BR \-500,2500 .
.TP
-.BI "\*-t " \fR[\fIlotime , \fR]\fIhitime
+.BI "\-t " \fR[\fIlotime , \fR]\fIhitime
Cut off interval output at the given time(s),
given in decimal seconds since 1970-01-01 00:00:00
Coordinated Universal Time (UTC).
.I timezone
determines whether the count includes leap seconds.
As with
-.BR \*-c ,
+.BR \-c ,
the cutoff's lower bound is inclusive and its upper bound is exclusive.
.SH "INTERVAL FORMAT"
The interval format is a compact text representation that is intended
where
.I string
is a double-quoted string giving the timezone, a second line
-.q "\*- \*- \fIinterval\fP"
+.q "\- \- \fIinterval\fP"
describing the time interval before the first transition if any, and
zero or more following lines
.q "\fIdate time interval\fP",
In times and in UT offsets with absolute value less than 100 hours,
the seconds are omitted if they are zero, and
the minutes are also omitted if they are also zero. Positive UT
-offsets are east of Greenwich. The UT offset \*-00 denotes a UT
+offsets are east of Greenwich. The UT offset \-00 denotes a UT
placeholder in areas where the actual offset is unspecified; by
convention, this occurs when the UT offset is zero and the time zone
abbreviation begins with
-.q "\*-"
+.q "\-"
or is
.q "zzz".
.PP
.nf
.sp
.if \n(.g .ft CR
-.in +2
+.if t .in +.5i
+.if n .in +2
.nr w \w'1896-01-13 'u+\n(.i
.ta \w'1896-01-13\0\0'u +\w'12:01:26\0\0'u +\w'-103126\0\0'u +\w'HWT\0\0'u
TZ="Pacific/Honolulu"
one can construct artificial time zones for which this fails.
.PP
In the
-.B \*-v
+.B \-v
and
-.B \*-V
+.B \-V
output,
.q "UT"
denotes the value returned by
.el .ds < \(la
.ie '\(ra'' .ds > >
.el .ds > \(ra
-.ie \n(.g \{\
-. ds : \:
-. ds - \f(CR-\fP
-.\}
-.el \{\
-. ds :
-. ds - \-
-.\}
+.ie \n(.g .ds : \:
+.el .ds : .
.ds d " degrees
.ds m " minutes
.ds s " seconds
If a
.I filename
is
-.q "\*-" ,
+.q "\-" ,
standard input is read.
.SH OPTIONS
.TP
-.B "\*-\*-version"
+.B "\-\-version"
Output version information and exit.
.TP
-.B \*-\*-help
+.B \-\-help
Output short usage message and exit.
.TP
-.BI "\*-b " bloat
+.BI "\-b " bloat
Output backward-compatibility data as specified by
.IR bloat .
If
as software that mishandles 64-bit data typically
mishandles timestamps after the year 2038 anyway.
Also see the
-.B \*-r
+.B \-r
option for another way to alter output size.
.TP
-.BI "\*-d " directory
+.BI "\-d " directory
Create time conversion information files in the named directory rather than
in the standard directory named below.
.TP
-.BI "\*-l " timezone
+.BI "\-l " timezone
Use
.I timezone
as local time.
If
.I timezone
is
-.BR \*- ,
+.BR \- ,
any already-existing link is removed.
.TP
-.BI "\*-L " leapsecondfilename
+.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
+.BI "\-p " timezone
Use
.IR timezone 's
rules when handling nonstandard
-TZ strings like "EET\*-2EEST" that lack transition rules.
+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
If
.I timezone
is
-.q "\*-"
+.q "\-"
(the default), any already-existing link is removed.
.sp
Unless
.I timezone is
-.q "\*-" ,
+.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"
+.B "\-b slim"
if
.IR timezone 's
transitions are at standard time or Universal Time (UT) instead of local time.
.TP
-.BR "\*-r " "[\fB@\fP\fIlo\fP][\fB/@\fP\fIhi\fP]"
+.BR "\-r " "[\fB@\fP\fIlo\fP][\fB/@\fP\fIhi\fP]"
Limit the applicability of output files
to timestamps in the range from
.I lo
(1970-01-01 00:00:00 UTC).
Omitted counts default to extreme values.
The output files use UT offset 0 and abbreviation
-.q "\*-00"
+.q "\-00"
in place of the omitted timestamp data.
For example,
-.q "zic \*-r @0"
+.q "zic \-r @0"
omits data intended for negative timestamps (i.e., before the Epoch), and
-.q "zic \*-r @0/@2147483648"
+.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 @$(date +%s)"
+.q "zic \-r @$(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
causes a TZif file to contain explicit entries for
.RI pre- hi
transitions rather than concisely representing them
-with an extended POSIX.1-2017 TZ string.
+with a proleptic TZ string.
Also see the
-.B "\*-b slim"
+.B "\-b slim"
option for another way to shrink output size.
.TP
-.BI "\*-R @" hi
+.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.1-2017 TZ string.
+more concisely represented via the proleptic TZ string.
This option does not affect the represented timestamps.
Although it accommodates nonstandard TZif readers
-that ignore the extended POSIX.1-2017 TZ string,
+that ignore the proleptic TZ string,
it increases the size of the altered output files.
.TP
-.BI "\*-t " file
+.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
+.B \-v
Be more verbose, and complain about the following situations:
.RS
.PP
.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.1-2017 TZ string. For example, as of 2023 this problem
+a proleptic 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.1-2017 TZ string cannot represent.
+a proleptic TZ string cannot represent.
.PP
The output contains data that may not be handled properly by client
code designed for older
The output contains a truncated leap second table,
which can cause some older TZif readers to misbehave.
This can occur if the
-.B "\*-L"
+.B "\-L"
option is used, and either an Expires line is present or
the
-.B "\*-r"
+.B "\-r"
option is also used.
.PP
The output file contains more than 1200 transitions,
at least 6.
.PP
An output file name contains a byte that is not an ASCII letter,
-.q "\*-" ,
+.q "\-" ,
.q "/" ,
or
.q "_" ;
or it contains a file name component that contains more than 14 bytes
or that starts with
-.q "\*-" .
+.q "\-" .
.RE
.SH FILES
Input files use the format described in this section; output files use
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
+.B \-v
option.
.PP
Input lines are made up of fields.
A rule line has the form
.nf
.ti +2
-.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
+.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
+Rule NAME FROM TO \- IN ON AT SAVE LETTER/S
.sp
For example:
.ti +2
.sp
-Rule US 1967 1973 \*- Apr lastSun 2:00w 1:00d D
+Rule US 1967 1973 \- Apr lastSun 2:00w 1:00d D
.sp
.fi
The fields that make up a rule line are:
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 \*-
+.q \-
nor
.q + .
To allow for future extensions,
.B FROM
field.
.TP
-.B \*-
+.B \-
Is a reserved field and should always contain
-.q \*-
+.q \-
for compatibility with older versions of
.BR zic .
It was previously known as the
.TP
.B IN
Names the month in which the rule takes effect.
-Month names may be abbreviated.
+Month names may be abbreviated as mentioned previously;
+for example, January can appear as
+.q January ,
+.q JANU
+or
+.q Ja ,
+but not as
+.q j
+which would be ambiguous with both June and July.
.TP
.B ON
Gives the day on which the rule takes effect.
.q "last"
(e.g.,
.BR "lastSunday" )
-may be abbreviated or spelled out in full.
+may be abbreviated as mentioned previously,
+e.g.,
+.q Su
+for Sunday and
+.q lastsa
+for the last Saturday.
There must be no white space characters within the
.B ON
field.
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
+\-2:30 2.5 hours before 00:00
+\- equivalent to 0
.fi
.in
.sp
.q "EDT" )
of time zone abbreviations to be used when this rule is in effect.
If this field is
-.q \*- ,
+.q \- ,
the variable part is null.
.PP
A zone line has the form
.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,
+alternatively, a field in the same format as a rule-line
+.B SAVE
+field,
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.
+Standard time applies if this field is
+.B \-
+or for timestamps occurring before any rule takes effect.
When an amount of time is given, only the sum of standard time and
this amount matters.
.TP
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.
+shows where to put the time zone abbreviation's variable part,
+which is taken from the
+.B LETTER/S
+field of the corresponding rule;
+any timestamps that precede the earliest rule use the
+.B LETTER/S
+of the earliest standard-time rule (which in this case must exist).
Alternatively, a format can use the pair of characters
.B %z
to stand for the UT offset in the form
alphanumeric ASCII characters,
.q "+"
and
-.q "\*-".
+.q "\-".
By convention, the time zone abbreviation
-.q "\*-00"
+.q "\-00"
is a placeholder that means local time is unspecified.
.TP
.B UNTIL
.ne 7
.nf
.in +2
-.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
+.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 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\0'u +\w'America/Menominee\0\0'u +\w'STDOFF\0\0'u +\w'RULES\0\0'u +\w'FORMAT\0\0'u
# Zone NAME STDOFF RULES FORMAT [UNTIL]
-Zone America/Menominee \*-5:00 \*- EST 1973 Apr 29 2:00
- \*-6:00 US C%sT
+Zone America/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).
+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).
+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
.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
+Zone Etc/GMT\0\00\0\0\-\0\0GMT
.sp
.in
.fi
.q "+"
if a second was added
or
-.q "\*-"
+.q "\-"
if a second was skipped.
The
.B R/S
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
+Rolling leap seconds would let one 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
+Although stationary leap seconds are the common practice,
+rolling leap seconds can be useful in specialized applications
+like SMPTE timecodes that may prefer to put leap second
+discontinuities at the end of a local broadcast day.
+However, rolling leap seconds are not supported if the
+.B \-r
option is used.
.PP
The expiration line, if present, has the form:
input, intended to illustrate many of its features.
.nf
.in +2
-.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
+.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 \*-
+# 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 \*-
+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
+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
projects / thirdparty / man-pages.git / commitdiff
