zic - time zone compiler
zic [ -v ] [ -d directory ] [ -l localtime ] [ -p posixrules ] [ -L
leapsecondfilename ] [ -s ] [ -y command ] [ filename ... ]
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 filename
is -, the standard input is read.
These options are available:
Create time conversion information files in the named directory
rather than in the standard directory named below.
Use the given time zone as local time. Zic will act as if the input
contained a link line of the form
Link timezone localtime
Use the given time zone's rules when handling POSIX-format time zone
environment variables. Zic will act as if the input contained a
link line of the form
Link timezone posixrules
Read leap second information from the file with the given name. If
this option is not used, no leap second information appears in
-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.
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. Non-blank
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
Rule US 1967 1973 - Apr lastSun 2:00 1:00
The fields that make up a rule line are:
NAME Gives the (arbitrary) name of the set of rules this rule is part
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
ON Gives the day on which the rule takes effect. Recognized forms
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
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
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).
Gives the "variable part" (for example, the "S" or "D" in "EST"
or "EDT") of time zone 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 GMTOFF RULES/SAVE FORMAT
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 time zone. This is the name used in creating the
time conversion information file for the zone.
The amount of time to add to GMT 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
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 - then standard time always applies in the time zone.
The format for time zone abbreviations in this time zone. The pair
of characters %s is used to show where the "variable part" of the
time zone abbreviation goes. Alternately, a slash (/) separates
standard and daylight abbreviations.
UNTIL The time at which the GMT 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 GMT offset and rule change until the time specified.
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
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
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
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 GMT or (an abbreviation of) "Rolling" if the leap second
time given by the other fields should be interpreted as local wall clock
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.
/usr/lib/zoneinfo Standard directory used for created files
ctime(3), tzfile(5), zdump(8).