zic - timezone compiler
] [ -d directory
] [ -l
] [ -p posixrules
] [ -L
] [ -s
] [ -y command
reads text from the file(s) named on the command line and creates the
time conversion information files specified in this input. If a
, the 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
- Complain if a year that appears in a data file is outside the range of
years representable by time(2) values.
- 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
Rule US 1967 1973 - Apr lastSun 2:00 1:00 D
The fields that make up a rule line are:
- Gives the (arbitrary) name of the set of rules this rule is part of.
- 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
- 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
- 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.
- Names the month in which the rule takes effect. Month names may be
- 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.
- Gives the time of day at which the rule takes effect. Recognized forms
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.
- 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
- 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]
Zone Australia/Adelaide 9:30 Aus CST 1971 Oct 31 2:00
The fields that make up a zone line are:
- The name of the timezone. This is the name used in creating the time
conversion information file for the zone.
- 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
- 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.
- 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.
- 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
- 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
Link Europe/Istanbul Asia/Istanbul
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
Leap 1974 Dec 31 23:59:60 + S
, 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.
- Standard directory used for created files.
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
This page is part of release 4.10 of the Linux man-pages
description of the project, information about reporting bugs, and the latest
version of this page, can be found at