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NAME
zic - timezone compiler
SYNOPSIS
zic [-v] [-d directory] [-l localtime] [-p posixrules]
[-L leapsecondfilename] [-s] [-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.
These options are available:
-d directory
Create time conversion information files in the named directory rather than in the standard
directory named below.
-l timezone
Use the given timezone as local time. zic will act as if the input contained a link line of the
form
Link timezone localtime
-p timezone
Use the given timezone's rules when handling POSIX-format timezone environment variables. zic
will act as if the input contained a link line of the form
Link timezone posixrules
-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.
-v Complain if a year that appears in a data file is outside the range of years representable by
time(2) values.
-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.
-y command
Use the given command rather than yearistype when checking year types (see below).
Input lines are made up of fields. Fields are separated from one another by any number of 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. Nonblank lines are
expected to be of one of three types: rule lines, zone lines, and link lines.
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 2:00 1:00 D
The fields that make up a rule line are:
NAME Gives the (arbitrary) name of the set of rules this rule is part of.
FROM Gives the first year in which the rule applies. Any integer year can be supplied; the Gregorian
calendar is assumed. The word minimum (or an abbreviation) means the minimum year representable
as an integer. The word 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.
TO Gives the final year in which the rule applies. In addition to minimum and maximum (as above),
the word only (or an abbreviation) may be used to repeat the value of the FROM field.
TYPE Gives the type of year in which the rule applies. If TYPE is -, then the rule applies in all
years between FROM and TO inclusive. If TYPE is something else, then zic executes the command
yearistype year type
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.
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. Note that there must be no spaces
within the ON field.
AT Gives the time of day at which the rule takes effect. Recognized forms include:
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
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 w if the given time is local "wall clock" time, s if the given
time is local "standard" time, or u (or g or z) if the given time is universal time; in the absence of an
indicator, wall clock time is assumed.
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 AT field (although, of course, the w and s suffixes are not
used).
LETTER/S
Gives the "variable part" (for example, the "S" or "D" in "EST" or "EDT") of timezone
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 UTCOFF RULES/SAVE FORMAT [UNTIL]
For example:
Zone Australia/Adelaide 9:30 Aus CST 1971 Oct 31 2:00
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 zone.
UTCOFF
The amount of time to add to UTC to get standard time in this zone. 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 UTC.
RULES/SAVE
The name of the rule(s) that apply in the timezone or, alternately, an amount of time to add to
local standard time. If this field is -, then standard time always applies in the timezone.
FORMAT
The format for timezone abbreviations in this timezone. The pair of characters %s is used to show
where the "variable part" of the timezone abbreviation goes. Alternately, a slash (/) separates
standard and daylight abbreviations.
UNTIL The time at which the UTC 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 timezone information is generated
from the given UTC 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 columns of a rule; trailing columns can be omitted,
and default to the earliest possible value for the missing columns.
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 field in the previous line in the file used by the previous line.
Continuation lines may contain an UNTIL field, just as zone lines do, indicating that the next line
is a further continuation.
A link line has the form
Link LINK-FROM LINK-TO
For example:
Link Europe/Istanbul Asia/Istanbul
The LINK-FROM field should appear as the NAME field in some zone line; the LINK-TO field is used as an
alternate name for that zone.
Except for continuation lines, lines may appear in any order in the input.
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 1974 Dec 31 23:59:60 + S
The YEAR, MONTH, DAY, and HH:MM:SS fields tell when the leap second happened. 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.
FILES
/usr/local/etc/zoneinfo
Standard directory used for created files.
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.
SEE ALSO
tzfile(5), zdump(8)
COLOPHON
This page is part of release 4.15 of the Linux man-pages project. A description of the project,
information about reporting bugs, and the latest version of this page, can be found at
https://www.kernel.org/doc/man-pages/.
2010-02-25 ZIC(8)