zic - Time zone compiler
/usr/bin/zic [-v] [-d directory] [-l localtime] [-p
posixrules] [-L leapsecondfilename] [-s] [-y commandname]
[filename...]
Create time conversion information files in the named
directory rather than in the standard directory. Use the
given time zone as local time. The zic compiler acts as
if the input contains a link line of the form: link timezone
localtime Use the given time zone's rules when handling
POSIX-format time zone environment variables. The
zic compiler acts as if the input contains a link line of
the form: Link timezone posixrules 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. Returns a warning if a year that appears in a data
file is outside the range of years representable by
time(3) values. Limit time values stored in output files
to values that are the same whether they are signed or
unsigned. You can use this option to generate SVVS-compatible
files. Use the given command rather than
yearistype when checking year types.
The zic compiler reads text from the file(s) named on the
command line and creates the time conversion information
files specified. If the filename parameter is specified as
a dash (-), the standard input is read. Timezone information
files are stored in the /etc/zoneinfo directory.
Input lines are made up of fields that are separated from
one another by any number of white space characters. Leading
and trailing white space is ignored. An unquoted number
sign (#) character in the input introduces a comment
which extends to the end of the line on which the number
sign # character appears. Enclose white space characters
and number sign # characters in double quotation marks ("
") if the characters are used as part of a field. Any line
that is blank (after comment stripping) is ignored. Nonblank
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 as follows: Gives
the (arbitrary) name of the set of rules of which this
rule is part. 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 with a representable time
value. The word "maximum" (or an abbreviation) means the
maximum year with a representable time value. Rules can
describe times that cannot be represented as time values,
with the unrepresentable times ignored. This allows rules
to be portable among hosts with differing time value
types. Gives the final year in which the rule applies.
In addition to the words "minimum" and "maximum", you can
use the word "only" to repeat the value of the FROM field.
Gives the type of year in which the rule applies. If TYPE
is a dash (-) then the rule applies in all years between
FROM and TO inclusive. If TYPE is something else, then
the zic complier executes the following command to check
the type of a year: yearistype year type
An exit status of zero indicates that the year is
of the given type; an exit status of one indicates
that the year is not of the given type. Names the
month in which the rule takes effect. You can
abbreviate month names. 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
You can abbreviate names of days of the week or
spelled them out in full. There must be no spaces
within the ON field. 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
You can follow any of these forms with the letter w
if the given time is local wall clock time, the
letter s if the given time is local standard time,
or the letter u (or g or z) if the given time is
universal time. In the absence of an indicator,
wall clock time is assumed. 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, the w and s suffixes are
not used). 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 a dash (-), the variable part is
null.
A zone line has the form:
Zone NAME GMTOFF RULES/SAVE FORMAT [UNTIL]
For example:
Zone Australia/Adelaide 9:30 Aus CST 1971 Oct
31 2:00
The fields that make up a zone line are: 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 GMT 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 GMT. 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 a dash
(-), then standard time always applies in the time zone.
The format for time zone abbreviations in this time zone.
Use a percent sign followed by the letter s (%s) to indicate
where the variable part of the time zone abbreviation
goes. Alternately, a slash (/) separates standard and daylight
abbreviations. The time at which the GMT 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 GMT 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 columns of a rule; trailing columns can
be omitted, and default to the earliest possible value for
the missing columns.
The next line must be a continuation line, which
has the same form as a zone line except that the
string Zone and the name are omitted. Continuation
lines can also contain an UNTIL field indicating
that the next line is a further continuation. The
following example shows two continutaion lines following
a zone line: # Zone NAME GMTOFF
RULES FORMAT [UNTIL] # Northern Territory Zone
Australia/Darwin 8:43:20 - LMT 1895 Feb
9:00 - CST
1899 May
9:30 Aus CST
A link line has the form:
Link LINK-FROM LINK-TO
For example:
Link Europe/Istanbul Asia/Istanbul
The LINK-FROM field appears 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 can appear in any
order.
Lines in the file that describe 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 is a plus sign (+) if
a second was added or a minus sign (-) if a second was
skipped. The R/S field is an abbreviation of Stationary
if the leap second time given by the other fields should
be interpreted as GMT or (an abbreviation of) Rolling if
the leap second time given by the other fields should be
interpreted as local wall clock time.
Note
For areas with more than two types of local time, you
might 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.
The following examples show how you use the time zone commands
and databases. You must be logged in as superuser
(root) to use the following commands: Use a procedure similar
to the following if a system is relocated to a new
timezone. This example uses Australian time zones and
shows what you need to do when relocating a host system
from from Brisbane (Queensland) to Sydney (New South
Wales): Verify the value of the link file /etc/zoneinfo/localtime
as follows: # ls -l /etc/zoneinfo/localtime
lrwxrwxrwx 1 root system 18 Mar 19 17:05 localtime ->
\ ./Australia/Queensland
If necessary, use the zdump command to verify transitions
in the target time zone as follows: #zdump -c 2001 -v Australia/NSW
Australia/NSW Fri Dec 13 20:45:52 1901 GMT =
Fri Dec 13 15:45:52 1901 EST \ isdst=0 gmtoff=-18000 Australia/NSW
Sat Dec 14 20:45:52 1901 GMT = Sat Dec 14
15:45:52 1901 EST \ isdst=0 gmtoff=-18000 Australia/NSW
Sun Mar 31 06:59:59 1918 GMT = Sun Mar 31 01:59:59 1918
EST \ isdst=0 gmtoff=-18000 Australia/NSW Sun Mar 31
07:00:00 1918 GMT = Sun Mar 31 03:00:00 1918 EWT \
isdst=1 gmtoff=-14400 Australia/NSW Sun Oct 27 05:59:59
1918 GMT = Sun Oct 27 01:59:59 1918 EWT \ isdst=1
gmtoff=-14400 . . . (output truncated) Delete the
/etc/zoneinfo/localtime link as follows: # rm /etc/zoneinfo/localtime
Create a new /etc/zoneinfo/localtime link, specifying the
target time zone as follows: # ln -s /etc/zoneinfo/Australia/NSW
localtime #ls -l localtime should now be:
localtime -> ./Australia/NSW check the transitions have
changed using zdump
Verify the new link as follows: # ls -l /etc/zoneinfo/localtime
lrwxrwxrwx 1 root system 18 Mar
19 17:05 /etc/zoneinfo/localtime -> \ ./Australia/NSW
Repeat the zdump command in Step b to verify transitions
in the target time zone. The system time
automatically changes for events such as Daylight
Savings Time. These time transitions are stored in
the /etc/zoneinfo database. If necessary, you can
verify and alter the rules that specify when a system
will automatically alter its time. This example
shows how you change the active /etc/zoneinfo file
to include the changes to Daylight Savings Time.
(Such a change was mandated for the 2000 Olympics,
moving the start date of Daylight Savings Time to
August 27th in 2000, rather than the expected date
of October 29th.)
The example assumes that the system is located in
Sydney, Australia: Examine the active time zone
setting as follows: # ls -l /etc/zoneinfo/localtime
lrwxrwxrwx root system 18 Mar 19 17:05 etc/zoneinfo/localtime
-> \ ./Australia/NSW
Use the zdump command to verify the time transitions
for the active time zone.
The zdump command prints transitions for every year
since the beginning of rules for the active timezone.
Use the more command or redirect (>) the output
to a file so you can find the relevent transition.
Use the -c option to specify the year at
which the display output terminates. For example: #
zdump -c 2002 -v Australia/NSW Australia/NSW Sat
Oct 30 15:59:59 1999 GMT = Sun Oct 31 01:59:59 1999
EST \ isdst=0 gmtoff=36000 Australia/NSW Sat Oct
30 16:00:00 1999 GMT = Sun Oct 31 03:00:00 1999 EST
\ isdst=1 gmtoff=39600 Australia/NSW Sat Mar 25
15:59:59 2000 GMT = Sun Mar 26 02:59:59 2000 EST \
isdst=1 gmtoff=39600 Australia/NSW Sat Mar 25
16:00:00 2000 GMT = Sun Mar 26 02:00:00 2000 EST \
isdst=0 gmtoff=36000 Australia/NSW Sat Oct 28
15:59:59 2000 GMT = Sun Oct 29 01:59:59 2000 EST \
isdst=0 gmtoff=36000 Australia/NSW Sat Oct 28
16:00:00 2000 GMT = Sun Oct 29 03:00:00 2000 EST \
isdst=1 gmtoff=39600
Each pair of lines for the same date and time shows
a time transition. On Sun Oct 29 2000 immediately
after 01:59:59 the time changes to 03:00:00. This
transition changes the local time from Australian
Eastern Standard Time (EST) to Daylight Savings
Time (DST). The value of the isdst field changes as
follows: 0 - Not Daylight Savings Time 1 - Daylight
Savings Time The gmtoff field displays the offset
from Greenwich Mean Time. Display the contents of
the /etc/zoneinfo database file for your locale to
find the rules for the local zone. In this case, it
is New South Wales: # more /etc/zoneinfo/sources/australasia
. . # New South Wales #
Rule NAME FROM TO TYPE IN ON AT
SAVE LETTER/S Rule AN 1971 1985 - Oct
lastSun 2:00s 1:00 - Rule AN 1972 only
- Feb 27 2:00s 0 - Rule AN
1973 1981 - Mar Sun>=1 2:00s 0 -
Rule AN 1982 only - Apr Sun>=1 2:00s
0 - Rule AN 1983 1985 - Mar
Sun>=1 2:00s 0 - Rule AN 1986 1989
- Mar Sun>=15 2:00s 0 - Rule AN
1986 only - Oct 19 2:00s 1:00 -
Rule AN 1987 1999 - Oct lastSun 2:00s
1:00 - Rule AN 1990 1995 - Mar
Sun>=1 2:00s 0 - Rule AN 1996 max
- Mar lastSun 2:00s 0 - # Zone NAME
GMTOFF RULES FORMAT [UNTIL] Zone Australia/Sydney
10:04:52 - LMT 1895 Feb
10:00 Aus EST
1971
10:00 AN EST Zone
Australia/Broken_Hill 9:25:48 - LMT 1895 Feb
10:00 - EST
1896 Aug 23
9:00 - CST
1899 May
9:30 Aus CST
1971
9:30 AN CST
2000
9:30 AS CST <display
truncated>
From this display, you find the rules that apply to
the current year. For the year 2000 the rules are
as follows: Rule AN 1996 max - Mar lastSun
2:00s 0 -
The other rules either end on a past year or apply
only for the year specified, as shown in the TO
column. The entry max in the TO column means that
the rule applies from the year listed in the FROM
column and for all future years. Assume that on
the last Sunday of October in 2000, you must change
the time at 2:00 a.m. to be one hour more than the
standard time (EST). On the last Sunday of March,
you must change the time at 3:00 a.m. to be the
same as EST, turning the clock back one hour when
the previous rule was active. (In this example,
the 27th happened to be the last Sunday in August,
making the transition change less complicated.) The
new rule that you must add is as follows: Rule
NAME FROM TO TYPE IN ON AT SAVE
LETTER/S Rule AN 2000 only -
Aug lastSun 2:00 1:00 -
To avoid corrupting the /etc/zoneinfo/sources/australasia
data file, copy it to a backup revision as
follows: # cp /etc/zoneinfo/sources/australasia
\ /etc/zoneinfo/sources/australasia.orig
Then edit the file /etc/zoneinfo/sources/australasia
with a text editor to add the following line:
Rule AN 2000 only - Aug lastSun
2:00 1:00 -
You can now use the zic command to update the
database with the new transition rule as follows: #
/usr/sbin/zic /etc/zoneinfo/sources/australasia
Use the zdump command to verify the new transitions
as follows: # zdump -c 2002 -v Australia/NSW . .
.Australia/NSW Sat Aug 26 15:59:59 2000 GMT = Sun
Aug 27 01:59:59 2000 \ EST isdst=0 gmtoff=36000
This truncated output indicates that the transition
to Daylight Savings Time moved from October 29 to
August 27, as required.
Standard directory used for created files Default script
used to determine type of year
Commands: zdump(8), settz(8)
Functions: ctime(3)
Files: tzfile(4)
zic(8)
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