ZIC(8) BSD System Manager's Manual ZIC(8)NAMEzic — time zone compiler
SYNOPSISzic [--version] [-d directory] [-L leapsecondfilename] [-l localtime]
[-p posixrules] [-s] [-v] [-y command] [Filename ...]
DESCRIPTIONzic 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:
--version Output version information and exit.
-d directory
Create time conversion information files in the named direc‐
tory rather than in the standard directory named below.
-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. zic will act as if
the input contained a link line of the form
Link timezone localtime
-p timezone
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
-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.
-v Complain if a year that appears in a data file is outside the
range of years representable by time(3) values. Also com‐
plain if a time of 24:00 (which cannot be handled by pre-1998
versions of zic) appears in the input.
-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 com‐
ment 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.
Names (such as month names) must be in English and are case
insensitive. Abbreviations, if used, must be unambiguous in
context.
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 Gives the (arbitrary) name of the set of rules this
rule is part of.
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 abbrevia‐
tion) means the maximum year representable 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 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 some‐
thing 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. Rec‐
ognized 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
- 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.
SAVE Gives the amount of time to be added to local stan‐
dard 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 [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 for‐
mat 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, alternatively, 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. Alternatively, 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 gener‐
ated 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 missing 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 pre‐
vious line. Continuation lines may contain until informa‐
tion, 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 alternative 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 fol‐
lowing 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 sec‐
ond 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 December 20, 2003 BSD