zic(8)
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ZIC(8) NetBSD System Manager's Manual ZIC(8)
NAME
zic -- time zone compiler
SYNOPSIS
zic [--version] [-d directory] [-L leapsecondfilename] [-l localtime]
[-p posixrules] [-s] [-v] [-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 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 Be more verbose, and complain about the following situations:
-
-
- Pre-1998 versions of zic(8) prohibit 24:00, and pre-2007
versions prohibit times greater than 24:00.
- Pre-2004 versions of zic(8) prohibit this.
- long-term future of a zone, because the future cannot be
summarized 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 calendar, which cannot be represented.
- code designed for older zic(8) output formats. These
compatibility issues affect only time stamps before 1970
or after the start of 2038.
- POSIX requires at least 3.
- ``-'', ``/'', or ``_''; or it or it contains a file name
component that contains more than 14 bytes or that starts
with ``-''.
-y command Use the given command rather than yearistype when checking
year types (see below).
Input files should be text files, that is, they should be a
series of zero or more lines, each ending in a newline byte
and containing at most 511 bytes, and without any NUL bytes.
The input text's encoding is typically UTF-8 or ASCII; it
should have a unibyte representation for the POSIX Portable
Character Set (PPCS) and the encoding's non-unibyte charac-
ters should consist entirely of non-PPCS bytes. Non-PPCS
characters typically occur only in comments: although output
file names and time zone abbreviations can contain nearly any
character, other software will work better if these are lim-
ited to the restricted syntax described under the [v] option.
Input lines are made up of fields. Fields are separated from
one another by one or more white space characters. The white
space characters are space, form feed, carriage return, new-
line, tab, and vertical tab. 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.
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 proleptic
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 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. The intent is that a rule line describes
the instants when a clock/calendar set to the type
of time specified in the AT field would show the
specified date and time of day.
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 abbre-
viations 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 AC%sT 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. It should not contain a file name
component ``''. or ``..''; a file name component
is a maximal substring that does not contain
``/''.
GMTOFF The amount of time to add to UT 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 UT.
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 UT 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 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 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 TARGET LINK-NAME
For example:
Link Europe/Istanbul Asia/Istanbul
The TARGET field should appear as the NAME field in some zone
line. The LINK-NAME field is used as an alternative name for
that zone; it has the same syntax as a zone line's NAME
field.
Except for continuation lines, lines may appear in any order
in the input. However, the behavior is unspecified if multi-
ple 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 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
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
0:29:44 - 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. 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 complete-
ness. 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 time zone 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 UT offset, zic produces a single transition to daylight saving
at the new UT offset (without any change in wall clock time). To get
separate transitions use multiple zone continuation lines specifying
transition instants using universal time.
Time stamps well before the Big Bang are silently omitted from the out-
put. This works around bugs in software that mishandles large negative
time stamps. Call it sour grapes, but pre-Big-Bang time stamps are phys-
ically suspect anyway. The pre-Big-Bang cutoff time is approximate and
may change in future versions.
FILES
/usr/share/zoneinfo - standard directory used for created files
SEE ALSO
ctime(3), tzfile(5), zdump(8)
NetBSD 7.1_STABLE October 6, 2014 NetBSD 7.1_STABLE
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