ZIC(8)ZIC(8)NAMEzic - time zone compiler
SYNOPSISzic [ --version ] [ -v ] [ -d directory ] [ -l localtime ] [ -p
posixrules ] [ -L leapsecondfilename ] [ -s ] [ -y command ] [ 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:
--version
Output version information and exit.
-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
-p timezone
Use the given time zone's rules when handling POSIX-format time
zone environment variables. Zic will act as if the input con‐
tained a link line of the form
Link timezone posixrules
-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 Be more verbose, and complain about the following situations:
The input data specifies a link to a link.
A year that appears in a data file is outside the range of years
representable by time(2) values.
A time of 24:00 or more appears in the input. Pre-1998 versions
of zic prohibit 24:00, and pre-2007 versions prohibit times
greater than 24:00.
A rule goes past the start or end of the month. Pre-2004 ver‐
sions of zic prohibit this.
The output file does not contain all the information about the
long-term future of a zone, because the future cannot be summa‐
rized as an extended POSIX TZ string. For example, as of 2013
this problem occurs for Iran's daylight-saving rules for the
predicted future, as these rules are based on the Iranian calen‐
dar, which cannot be represented.
The output contains data that may not be handled properly by
client code designed for older zic output formats. These com‐
patibility issues affect only time stamps before 1970 or after
the start of 2038.
A time zone abbreviation has fewer than 3 characters. POSIX
requires at least 3.
-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.
-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 one or more 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 char‐
acters 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 insensi‐
tive. 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 repre‐
sentable 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 por‐
table 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 abbrevia‐
tion) 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 inclu‐
sive. 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. Recog‐
nized 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 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 [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 UT 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 UT.
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 UT offset or the rule(s) change for a loca‐
tion. 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 UT 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. However, the behavior is unspecified if multiple zone or link
lines define the same name, or if the source of one link line is the
target of another.
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 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 1941 1942 - May Mon>=1 1:00 1:00 S
Rule Swiss 1941 1942 - Oct Mon>=1 2:00 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/SAVE FORMAT UNTIL
Zone Europe/Zurich 0:34:08 - LMT 1853 Jul 16
0:29:46 - 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. This example says that Zurich was 34 minutes and 8
seconds west of UT until 1853-07-16 at 00:00, when the legal offset was
changed to 7°26′22.50″; although this works out to 0:29:45.50, the
input format cannot represent fractional seconds so it is rounded here.
After 1894-06-01 at 00:00 Swiss daylight saving rules (defined with
lines beginning with "Rule Swiss") apply, and the UT 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 1941 and 1942, daylight saving time applied from the first Monday in
May at 01:00 to the first Monday in October at 02:00. The pre-1981 EU
daylight-saving rules have no effect here, but are included for com‐
pleteness. 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 com‐
piled 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 UT offset, zic produces a single transition to daylight sav‐
ing at the new UT offset (without any change in wall clock time). To
get separate transitions use multiple zone continuation lines specify‐
ing transition instants using universal time.
FILE
/usr/local/etc/zoneinfo standard directory used for created
files
SEE ALSOnewctime(3), tzfile(5), zdump(8)ZIC(8)
