.TH ZIC 8
.SH NAME
zic \- time zone compiler
.SH SYNOPSIS
.B zic
[
.B \-\-version
]
[
.B \-v
] [
.B \-d
.I directory
] [
.B \-l
.I localtime
] [
.B \-p
.I posixrules
] [
.B \-L
.I leapsecondfilename
] [
.B \-s
] [
.B \-y
.I command
] [
.I filename
\&... ]
.SH DESCRIPTION
.if t .ds lq ``
.if t .ds rq ''
.if n .ds lq \&"\"
.if n .ds rq \&"\"
.de q
\\$3\*(lq\\$1\*(rq\\$2
..
.I Zic
reads text from the file(s) named on the command line
and creates the time conversion information files specified in this input.
If a
.I filename
is
.BR \- ,
the standard input is read.
.PP
These options are available:
.TP
.BI "\-\-version"
Output version information and exit.
.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 the given time zone as local time.
.I Zic
will act as if the input contained a link line of the form
.sp
.ti +.5i
Link \fItimezone\fP localtime
.TP
.BI "\-p " timezone
Use the given time zone's rules when handling POSIX-format
time zone environment variables.
.I Zic
will act as if the input contained a link line of the form
.sp
.ti +.5i
Link \fItimezone\fP posixrules
.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
.B \-v
Be more verbose, and complain about the following situations:
.RS
.PP
The input data specifies a link to a link.
.PP
A year that appears in a data file is outside the range
of years representable by
.IR time (2)
values.
.PP
A time of 24:00 or more appears in the input.
Pre-1998 versions of
.I 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
.I zic
prohibit this.
.PP
The output file does not contain all the information about the
long-term future of a zone, because the future cannot be summarized as
an extended POSIX TZ string. For example, as of 2013 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.
.PP
The output contains data that may not be handled properly by client
code designed for older
.I zic
output formats. These compatibility issues affect only time stamps
before 1970 or after the start of 2038.
.PP
A time zone abbreviation has fewer than 3 characters.
POSIX requires at least 3.
.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.
.TP
.BI "\-y " command
Use the given
.I command
rather than
.B yearistype
when checking year types (see below).
.PP
Input lines are made up of fields.
Fields are separated from one another by one or more white space characters.
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.
Non-blank lines are expected to be of one of three types:
rule lines, zone lines, and link lines.
.PP
Names (such as month names) must be in English and are case insensitive.
Abbreviations, if used, 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'TYPE\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 TYPE IN ON AT SAVE LETTER/S
.sp
For example:
.ti +.5i
.sp
Rule US 1967 1973 \- Apr lastSun 2:00 1:00 D
.sp
.fi
The fields that make up a rule line are:
.TP "\w'LETTER/S'u"
.B NAME
Gives the (arbitrary) name of the set of rules this rule is part of.
.TP
.B FROM
Gives the first year in which the rule applies.
Any integer year can be supplied; the Gregorian calendar is assumed.
The word
.B minimum
(or an abbreviation) means the minimum year representable as an integer.
The word
.B maximum
(or an abbreviation) means the maximum year representable as an integer.
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 TYPE
Gives the type of year in which the rule applies.
If
.B TYPE
is
.B \-
then the rule applies in all years between
.B FROM
and
.B TO
inclusive.
If
.B TYPE
is something else, then
.I zic
executes the command
.ti +.5i
\fByearistype\fP \fIyear\fP \fItype\fP
.br
to check the type of a year:
an exit status of zero is taken to mean that the year is of the given type;
an exit status of one is taken to mean that the year is not of the given type.
.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
Names of days of the week may be abbreviated or spelled out in full.
Note that there must be no spaces within the
.B ON
field.
.TP
.B AT
Gives the time of day at which the rule takes effect.
Recognized forms include:
.nf
.in +.5i
.sp
.ta \w'1:28:13\0\0'u
2 time in hours
2:00 time in hours and minutes
15:00 24-hour format time (for times after noon)
1:28:14 time in hours, minutes, and seconds
\- 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.
Any of these forms may be followed by the letter
.B w
if the given time is local
.q "wall clock"
time,
.B s
if the given time is local
.q standard
time, or
.B u
(or
.B g
or
.BR z )
if the given time is universal time;
in the absence of an indicator,
wall clock time is assumed.
.TP
.B SAVE
Gives the amount of time to be added to local standard time when the rule is in
effect.
This field has the same format as the
.B AT
field
(although, of course, the
.B w
and
.B s
suffixes are not used).
.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
.BR \- ,
the variable part is null.
.PP
A zone line has the form
.sp
.nf
.ti +.5i
.ta \w'Zone\0\0'u +\w'Australia/Adelaide\0\0'u +\w'GMTOFF\0\0'u +\w'RULES/SAVE\0\0'u +\w'FORMAT\0\0'u
Zone NAME GMTOFF RULES/SAVE FORMAT [UNTILYEAR [MONTH [DAY [TIME]]]]
.sp
For example:
.sp
.ti +.5i
Zone Australia/Adelaide 9:30 Aus CST 1971 Oct 31 2:00
.sp
.fi
The fields that make up a zone line are:
.TP "\w'GMTOFF'u"
.B NAME
The name of the time zone.
This is the name used in creating the time conversion information file for the
zone.
.TP
.B GMTOFF
The amount of time to add to UT to get standard time in this zone.
This field has the same format as the
.B AT
and
.B SAVE
fields of rule lines;
begin the field with a minus sign if time must be subtracted from UT.
.TP
.B RULES/SAVE
The name of the rule(s) that apply in the time zone or,
alternately, an amount of time to add to local standard time.
If this field is
.B \-
then standard time always applies in the time zone.
.TP
.B FORMAT
The format for time zone abbreviations in this time zone.
The pair of characters
.B %s
is used to show where the
.q "variable part"
of the time zone abbreviation goes.
Alternately,
a slash (/)
separates standard and daylight abbreviations.
.TP
.B UNTILYEAR [MONTH [DAY [TIME]]]
The time at which the UT offset or the rule(s) change for a location.
It is specified as a year, a month, a day, and a time of day.
If this is specified,
the time zone information is generated from the given UT offset
and rule change until the time specified.
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
A link line has the form
.sp
.nf
.ti +.5i
.ta \w'Link\0\0'u +\w'Europe/Istanbul\0\0'u
Link LINK-FROM LINK-TO
.sp
For example:
.sp
.ti +.5i
Link Europe/Istanbul Asia/Istanbul
.sp
.fi
The
.B LINK-FROM
field should appear as the
.B NAME
field in some zone line;
the
.B LINK-TO
field is used as an alternate name for that 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, 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:
.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 1974 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.
.\" There's no need to document the following, since it's impossible for more
.\" than one leap second to be inserted or deleted at a time.
.\" The C Standard is in error in suggesting the possibility.
.\" See Terry J Quinn, The BIPM and the accurate measure of time,
.\" Proc IEEE 79, 7 (July 1991), 894-905.
.\" or
.\" .q ++
.\" if two seconds were added
.\" or
.\" .q --
.\" if two seconds were 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.
.SH "EXTENDED EXAMPLE"
Here is an extended example of
.I zic
input, intended to illustrate many of its features.
.br
.ne 22
.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'TYPE\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 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 -
.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'GMTOFF\0\0'u +\w'RULES/SAVE\0\0'u +\w'FORMAT\0\0'u
# Zone NAME GMTOFF RULES/SAVE FORMAT UNTIL
Zone Europe/Zurich 0:34:08 - LMT 1853 Jul 16
0:29:46 - BMT 1894 Jun
1:00 Swiss CE%sT 1981
1:00 EU CE%sT
.sp
Link Europe/Zurich Switzerland
.sp
.in
.fi
In this example, the zone is named Europe/Zurich but it has an alias
as Switzerland. This example says that Zurich was 34 minutes and 8
seconds west 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 Swiss daylight saving rules
(defined with lines beginning with "Rule Swiss") apply, and the UT offset
became one hour. 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, "LMT" and "BMT" were initially used, respectively. Since
Swiss rules and later EU rules were applied, the display name for the
timezone has been CET for standard time and CEST for daylight saving
time.
.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 zone,
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,
.IR zic
produces a single transition to daylight saving at the new UT offset
(without any change in wall clock time).
To get separate transitions
use multiple zone continuation lines
specifying transition instants using universal time.
.SH FILE
/usr/local/etc/zoneinfo standard directory used for created files
.SH "SEE ALSO"
newctime(3), tzfile(5), zdump(8)
.\" This file is in the public domain, so clarified as of
.\" 2009-05-17 by Arthur David Olson.