TIMEZONE(4)                          SysV                          TIMEZONE(4)



NAME
     timezone - set default system time zone

SYNOPSIS
     /etc/TIMEZONE

DESCRIPTION
     When present, the file /etc/TIMEZONE is a Bourne shell script that sets
     and exports the time zone environmental variable TZ.  Procedures needing
     this information can read and execute this file by way of the Bourne
     shell's "dot" command.

     TZ allows you to specify a main local time zone and an alternate time
     zone, which, in practice, is usually Daylight Savings Time.  TZ also lets
     you specify the day and hour of the start and end of the alternate time
     zone.  TZ has the following syntax:

          TZ:            zone
                         zone { + | - } time
                         zone { + | - } time zone
                         zone { + | - } time zone dst

                         The first occurrence of zone specifies the main time
                         zone; the second specifies the alternate time zone.
                         The time specifies the time difference between GMT
                         (Greenwich Mean Time) and the main time zone.  A
                         minus sign (-) indicates time zones east of
                         Greenwich; the plus sign (+) is optional for time
                         zones west of Greenwich.

          zone:          letter letter letter

          time:          hour
                         hour : minute
                         hour : minute : second

          dst:           { + | - } time
                         { + | - } time { ; | , } dst_date , dst_date
                         { ; | , } dst_date , dst_date

                         The time specifies the time difference between GMT
                         and the alternate time zone.  A minus sign (-)
                         indicates time zones east of Greenwich; the plus sign
                         (+) is optional for time zones west of Greenwich.

                         The first occurrence of dst_date specifies the day
                         (and optionally, the time) on which the alternate
                         time zone begins; the second occurrence of dst_date
                         specifies the day (and optionally, the time) on which
                         the alternate time zone ends.  You may use either a
                         comma (,) or semicolon (;) to delimit the first
                         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

EXAMPLES
     On the Atlantic coast of the United States, you might want

          TZ=EST5EDT

     where EST is the abbreviation for the standard time zone, 5 is the
     difference, in hours, between GMT and the standard time zone, and EDT is
     the abbreviation for the alternate time zone.  An /etc/TIMEZONE file
     containing these lines would set TZ to this value:

          # Time Zone
          TZ=EST5EDT
          export TZ

     The most restrictive representation of the same setting for 1986 is:

          TZ="EST5:00:00EDT4:00:00;117/2:00:00,299/2:00:00"

     The components of this string corresponding to the syntax described above
     are as follows:

          EST       Abbreviation for the main time zone.

          5:00:00   The difference, in hours, minutes, and seconds between GMT
                    and the standard time zone.

          EDT       The abbreviation for the alternate time zone.

          4:00:00   The difference, in hours, minutes, and seconds between GMT
                    and the alternate time zone.

          117       Julian day (day of the year) when the alternate time zone
                    will take effect.

          2:00:00   The number of hours, minutes, and seconds past midnight
                    when the alternate time zone will take effect.

          299       Julian day when the alternate time zone will end.

          2:00:00   The number of hours, minutes, and seconds past mighnight
                    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 nine hours
     and 30 minutes 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.

SEE ALSO
     tz(1), ctime(3C), profile(4), environ(5).

NOTES

     On Apollo workstations, TZ is initialized at boot time from data written
     on the disk by tz(1).  To assign a different value to TZ, you may create
     your own /etc/TIMEZONE for use in the appropriate initialization
     procedures (/etc/profile, for example).

     When the longer format is used, the value assigned to TZ must be
     surrounded by double quotation marks.

     The Julian start and end days change from year to year.

     Setting the time to be within the interval between the end of the main
     time zone and the beginning of the alternate time zone, or vice versa, is
     not recommended.  (For example, on the morning Daylight Savings Time is
     scheduled to begin, don't set the time to be within the hour "lost").