TIMEZONE(4) TIMEZONE(4)
NAME
timezone - set default system time zone
SYNOPSIS
/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.
The syntax of TZ can be described as follows:
TZ -> zone
| zone signed_time
| zone signed_time zone
| zone signed_time zone dst
zone -> letter letter letter
signed_time -> sign time
| time
time -> hour
| hour : minute
| hour : minute : second
dst -> signed_time
| signed_time ; dst_date , dst_date
| ; dst_date , dst_date
dst_date -> julian
| julian / time
letter -> a | A | b | B | ... | z | Z
hour -> 00 | 01 | ... | 23
minute -> 00 | 01 | ... | 59
second -> 00 | 01 | ... | 59
julian -> 001 | 002 | ...| 366
sign -> - | +
EXAMPLES
The contents of /etc/TIMEZONE corresponding to the simple
example below could be
Page 1 May 1989
TIMEZONE(4) TIMEZONE(4)
# Time Zone
TZ=EST5EDT
export TZ
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
Page 2 May 1989
TIMEZONE(4) TIMEZONE(4)
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(4)).
NOTES
When the longer format is used, the TZ variable must be
surrounded by double quotes as shown.
The system administrator must change the Julian start and
end days annually if the longer form of the TZ variable is
used.
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.
FILES
/etc/timezone
SEE ALSO
rc2(1M), profile(4), environ(5).
ctime(3C) in the Programmer's Reference Manual.
Page 3 May 1989