zic - time zone compiler
zic [ -v ] [ -d directory ] [ -l localtime ] [ 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
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 file contained a
link line of the form
Link timezone localtime
-v Complain if a year that appears in a data file is outside the range of years repre-
sentable by time(2) values.
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 LETTER/S
Rule USA 1969 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. The word minimum (or an abbrevia-
tion) means the minimum year with a representable time value. The word maximum
(or an abbreviation) means the maximum year with a representable time value.
TO Gives the final year in which the rule applies. In addition to minimum and maxi-
mum (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 year applies. If TYPE is - then the rule
applies in all years between FROM and TO inclusive; if TYPE is uspres, the rule
applies in U.S. Presidential election years; if TYPE is nonpres, the rule applies
in years other than U.S. Presidential election years. 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 affect. 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
Any of these forms may be followed by the letter w if the given time is local
``wall clock'' time or s if the given time is local ``standard'' time; in the
absence of w or s, 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 [UNTIL]
Zone Australia/South-west 9:30 Aus CST 1987 Mar 15 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 from GMT.
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.
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 pre-
vious 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 con-
A link line has the form
Link LINK-FROM LINK-TO
Link US/Eastern EST5EDT
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.
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 transi-
tion time recorded in the compiled file is correct.
/usr/share/zoneinfostandard directory used for created files
newctime(3), tzfile(5), zdump(8)