ZIC(8) BSD System Manager's Manual ZIC(8)NAMEzic — timezone compiler
SYNOPSISzic [--version] [-Dsv] [-d directory] [-g group] [-L leapsecondfilename]
[-l localtime] [-m mode] [-p posixrules] [-u user] [-y command]
[filename ...]
DESCRIPTION
The zic utility 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.
The following options are available:
--version
Output version information and exit.
-D Do not automatically create directories. If the input file(s)
specify an output file in a directory which does not already
exist, the default behavior is to attempt to create the direc‐
tory. If -D is specified, zic will instead error out immedi‐
ately.
-d directory
Create time conversion information files in the named directory
rather than in the standard directory named below.
-g group
After creating each output file, change its group ownership to
the specified group (which can be either a name or a numeric
group ID).
-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.
-l timezone
Use the given time zone as local time. The zic utility will act
as if the input contained a link line of the form
Link timezone localtime
(Note that this action has no effect on FreeBSD, since the local
time zone is specified in /etc/localtime and not
/usr/share/zoneinfo/localtime.)
-m mode
After creating each output file, change its access mode to mode.
Both numeric and alphabetic modes are accepted (see chmod(1)).
-p timezone
Use the given time zone's rules when handling POSIX-format time
zone environment variables. The zic utility will act as if the
input contained a link line of the form
Link timezone posixrules
-u user
After creating each output file, change its owner to user (which
can be either a name or a numeric user ID).
-v Complain if a year that appears in a data file is outside the
range of years representable by time(3) values.
-s Limit time values stored in output files to values that are the
same whether they are 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 are 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 US 1967 1973 - Apr lastSun 2:00 1:00 D
The fields that make up a rule line are:
NAME Give the (arbitrary) name of the set of rules this rule
is part of.
FROM Give the first year in which the rule applies. Any inte‐
ger 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 rep‐
resentable as an integer. Rules can describe times that
are not representable as time values, with the unrepre‐
sentable times ignored; this allows rules to be portable
among hosts with differing time value types.
TO Give the final year in which the rule applies. In addi‐
tion to minimum and maximum (as above), the word only (or
an abbreviation) may be used to repeat the value of the
FROM field.
TYPE Give 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 exe‐
cutes 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 Name the month in which the rule takes effect. Month
names may be abbreviated.
ON Give 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 Give 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
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 indi‐
cator, wall clock time is assumed.
SAVE Give 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 Give 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 [UNTILYEAR [MONTH [DAY
[TIME]]]]
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 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 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 time zone or, alter‐
nately, 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. Alternately, a slash (/)
separates standard and daylight abbreviations.
UNTILYEAR [MONTH [DAY [TIME]]]
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 time zone information is gen‐
erated 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 fields of a rule; trailing fields can be
omitted, and default to the earliest possible value for the miss‐
ing fields.
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 information in the
previous line in the file used by the previous line. Continua‐
tion lines may contain until information, 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 hap‐
pened. 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.
EXTENDED EXAMPLE
Here is an extended example of zic input, intended to illustrate many of
its features.
# Rule NAME FROM TO TYPE IN ON AT SAVE LETTER/S
Rule Swiss 1940 only - Nov 2 0:00 1:00 S
Rule Swiss 1940 only - Dec 31 0:00 0 -
Rule Swiss 1941 1942 - May Sun>=1 2:00 1:00 S
Rule Swiss 1941 1942 - Oct Sun>=1 0:00 0
Rule EU 1977 1980 - Apr Sun>=1 1:00u 1:00 S
Rule EU 1977 only - Sep lastSun 1:00u 0 -
Rule EU 1978 only - Oct 1 1:00u 0 -
Rule EU 1979 1995 - Sep lastSun 1:00u 0 -
Rule EU 1981 max - Mar lastSun 1:00u 1:00 S
Rule EU 1996 max - Oct lastSun 1:00u 0 -
# Zone NAME GMTOFF RULES FORMAT UNTIL
Zone Europe/Zurich 0:34:08 - LMT 1848 Sep 12
0:29:44 - BMT 1894 Jun
1:00 Swiss CE%sT 1981
1:00 EU CE%sT
Link Europe/Zurich Switzerland
In this example, the zone is named Europe/Zurich but it has an alias as
Switzerland. Zurich was 34 minutes and 8 seconds west of GMT until
1848-09-12 at 00:00, when the offset changed to 29 minutes and 44 sec‐
onds. After 1894-06-01 at 00:00 Swiss daylight saving rules (defined
with lines beginning with "Rule Swiss") apply, and the GMT offset became
one hour. From 1981 to the present, EU daylight saving rules have
applied, and the UTC offset has remained at one hour.
In 1940, daylight saving time applied from November 2 at 00:00 to Decem‐
ber 31 at 00:00. In 1941 and 1942, daylight saving time applied from the
first Sunday in May at 02:00 to the first Sunday in October at 00:00.
The pre-1981 EU daylight-saving rules have no effect here, but are
included for completeness. Since 1981, daylight saving has begun on the
last Sunday in March at 01:00 UTC. Until 1995 it ended the last Sunday
in September at 01:00 UTC, but this changed to the last Sunday in October
starting in 1996.
For purposes of display, "LMT" and "BMT" were initially used, respec‐
tively. Since Swiss rules and later EU rules were applied, the display
name for the timezone has been CET for standard time and CEST for day‐
light saving time.
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.
If, for a particular zone, a clock advance caused by the start of day‐
light saving coincides with and is equal to a clock retreat caused by a
change in UTC offset, zic produces a single transition to daylight saving
at the new UTC offset (without any change in wall clock time). To get
separate transitions use multiple zone continuation lines specifying
transition instants using universal time.
FILES
/usr/share/zoneinfo standard directory used for created files
SEE ALSOctime(3), tzfile(5), zdump(8)BSD June 20, 2004 BSD
