TIMEZONE(F) UNIX System V
Name
timezone - set default system time zone
Syntax
/etc/TIMEZONE
Description
This file sets and exports the time zone environmental
variable TZ.
This file is ``dotted'' into other files that must know the
time zone, including /etc/cshrc, /etc/profile, /etc/rc2,
.profile.
TZ contains the following information:
(sss) One to nine letters designating the standard
time zone.
(n) Number of hours past Greenwich mean time for the
standard time (partial hours are valid e.g.
12:30:01). Positive hours are west of Greenwich,
negative numbers are east of Greeenwich.
(ddd) One to nine letters designating the local
daylight savings time (summer time) zone. If not
present, summer time is assumed not to apply.
(m) Number of hours past Greenwich mean time for the
summer time (partial hours are valid e.g.
11:30:01). Positive hours are west of
Greenwich, negative numbers are east of
Greeenwich. If m is not given, the distance to
GMT during summer time is assumed to be one hour
less than during standard time.
(start) The rule defining the day summer time begins.
In the southern hemisphere, the ending day will
be earlier in the year than the starting day.
(end) The rule defining the day summer time ends.
(time) The time of day the change to and from summer
time occurs. The default is 02:00:00 local time.
The rules for defining the start and end of summer time are
as follows:
Jn 1 based Julian day n (1 < n < 365)*
n 0 based Julian day n (0 < n < 364)*
Wn.d day d (0 < d < 6)** of week n (1 < n < 53)†
Mm.n.d day d of week n (1 < n < 5)‡ of month m (1 < m < 12)
* Leap days (February 29) are never counted; that is,
February 28 (J59) is immediately followed by March 1
(J60) even in leap years.
** Sunday is the first day of the week (0). If d is omitted,
Sunday is assumed. Note that d is optional.
† The 5th week of the month is always the last week
containing day d, whether there are actually 4 or 5 weeks
containing day d.
‡ The 53rd week of the year is always the last week
containing day d, whether there are actually 52 or 53
weeks containing day d.
If start and end are omitted, current U.S. law is assumed.
Examples
A simple setting for New Jersey could be
TZ='EST5EDT'
where
EST is the abbreviation for the main time zone, 5 is the
difference, in hours, between GMT (Greenwich Mean Time) and
the main time zone, and
EDT is the abbreviation for the alternate time zone.
The most complex representation of the same setting, for the
year 1986, is
TZ='EST5:00:00EDT4:00:00;117/2:00:00,299/2:00:00'
where
EST is the abbreviation for the main time zone, 5:00:00 is
the difference, in hours, minutes, and seconds between GMT
and the main time zone,
EDT is the abbreviation for the alternate time zone, 4:00:00
is the difference, in hours, minutes, and seconds between
GMT and the alternate time zone, 117 is the number of the
day of the year (Julian day) when the alternate time zone
will take effect, 2:00:00 is the number of hours, minutes,
and seconds past midnight when the alternate time zone will
take effect, 299 is the number of the day of the year when
the alternate time zone will end, and 2:00:00 is the number
of hours, minutes, and seconds past midnight when the
alternate time zone will end.
A southern hemisphere setting such as the Cook Islands could
be
TZ='KDT9:30KST10:00;64/5:00,303/20:00'
This setting means that
KDT is the abbreviation for the main time zone,
KST is the abbreviation for the alternate time zone, KST is
9 hours and 30 minutes later than GMT, KDT is 10 hours later
than GMT, the starting date of KDT is the 64th day at 5 AM,
and the ending date of KDT is the 303rd day at 8 PM.
Starting and ending times are relative to the alternate time
zone. If the alternate time zone start and end dates and
the time are not provided, the days for the United States
that year will be used and the time will be 2 AM. If the
start and end dates are provided but the time is not
provided, the time will be midnight.
Note that in most installations,
TZ is set to the correct value by default when the user logs
on, via the local /etc/profile file [see profile(F)].
See Also
ctime(S), profile(F), environ(M), TZ(M), rc2(ADM)
Notes
Setting the time during the interval of change from the main
time zone to the alternate time zone or vice versa can
produce unpredictable results.
Standards Conformance
timezone is conformant with:
The X/Open Portability Guide II of January 1987.
(printed 8/23/89) TIMEZONE(F)