||FreeBSD System Manager's Manual
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:
- Output version information and exit.
- 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 directory. If
-D is specified,
instead error out immediately.
- Create time conversion information files in the named directory rather
than in the standard directory named below.
- After creating each output file, change its group ownership to the
specified group (which can be either a name or a
numeric group ID).
- Read leap second information from the file with the given name. If this
option is not used, no leap second information appears in output
- 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
- After creating each output file, change its access mode to
mode. Both numeric and alphabetic modes are accepted
- 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
- After creating each output file, change its owner to
user (which can be either a name or a numeric user
- Complain if a year that appears in a data file is outside the range of
years representable by
- 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.
- 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.
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
Rule US 1967 1973 - Apr lastSun 2:00 1:00 D
The fields that make up a rule line are:
- Give the (arbitrary) name of the set of rules this rule is part of.
- Give 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
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 portable among
hosts with differing time value types.
- Give 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.
- 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
executes the command
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.
- Name the month in which the rule takes effect. Month names may be
- Give the day on which the rule takes effect. Recognized forms include:
- the fifth of the month
- the last Sunday in the month
- the last Monday in the month
- first Sunday on or after the eighth
- 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
- Give the time of day at which the rule takes effect. Recognized forms
- time in hours
- time in hours and minutes
- 24-hour format time (for times after noon)
- 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
z’) if the given time is
universal time; in the absence of an indicator, wall clock time is
- 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 ‘
s’ suffixes are not used).
- 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]]]]
The fields that make up a zone line are:
Zone Australia/Adelaide 9:30 Aus CST 1971 Oct 31
- 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 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.
- 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
- 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 generated 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 previous line. Continuation 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
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.
Link Europe/Istanbul Asia/Istanbul
Except for continuation lines, lines may appear in any order in
Lines in the file that describes leap seconds have the following
Leap YEAR MONTH DAY HH:MM:SS CORR R/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.
Here is an extended example of
Leap 1974 Dec 31 23:59:60 + S
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 seconds. 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
December 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
For purposes of display, "LMT" and "BMT" were
initially used, respectively. Since Swiss rules and later EU rules were
applied, the display name for the timezone has been CET for standard time
and CEST for daylight saving time.
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
daylight 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.
- standard directory used for created files
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