NAME
zic - time zone compiler

SYNOPSIS
zic [ -v ] [ -d directory ] [ -l localtime ]
[ -L leapsecondfilename ] [ -s ] [ filename ... ]

DESCRIPTION
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:

-d directory
Create time conversion information files in the named
directory rather than in the standard directory named below.

-l timezone
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

-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.

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

For example:

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 abbreviation) 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 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 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 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

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).

LETTER/S
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]

For example:

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.

GMTOFF
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.

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 - then standard time always applies in the
time zone.

FORMAT
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 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 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.

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 GMT or (an abbreviation of)
"Rolling" if the leap second time given by the other fields should
be interpreted as local wall clock time.

NOTE
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.

FILES
/usr/etc/zoneinfo standard directory used for created files