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TZ(5)                         File Formats Manual                        TZ(5)

NAME
       TZ - Time zone environment variable

SYNOPSIS
       TZ=zone[-]offset[dst[offset][,start[/time],end[/time]]]

DESCRIPTION
       The TZ environment variable tells functions such as the ctime(3) family
       and programs like date what the time zone and daylight saving rule  is.
       The  value of TZ has the POSIX standardized form shown in the synopsis.
       This form specifies the zone names,  offsets  from  GMT,  and  daylight
       saving changeover times for at least the current year.

       zone   A three or more letter name for the time zone in normal (winter)
              time.

       [-]offset
              A signed time telling the offset of the time zone westwards from
              Greenwich.  The time has the form hh[:mm[:ss]] with a one or two
              digit hour, and optional two digit minutes and seconds.

       dst    The name of the time zone when daylight saving is in effect.  It
              may  be  followed  by  an  offset  telling  how  big  the  clock
              correction is other than the default of 1 hour.

       start/time,end/time
              Specifies the start and end of the daylight saving period.   The
              start and end fields indicate on what day the changeover occurs.
              They must be in one of the following formats:

              Jn   The Julian day n (1 <= n <= 365) ignoring leap  days,  i.e.
                   there is no February 29.

              n    The  zero-based  Julian day (0 <= n <= 365).  Leap days are
                   not ignored.

              Mm.n.d
                   This indicates month m, the n-th occurrence of day d (1  <=
                   m  <=  12,  1  <= n <= 5, 0 <= d <= 6, 0=Sunday).  The 5-th
                   occurrence means the last  occurrence  of  that  day  in  a
                   month.   So  M4.1.0 is the first Sunday in April, M9.5.0 is
                   the last Sunday in September.

              The time field indicates the time the changeover occurs  on  the
              given day.

EXAMPLES
       Greenwich Mean Time:

              TZ='GMT0'

       Central  European  Time,  1  hour  east from Greenwich, daylight saving
       starts on the last Sunday in March at 2 AM and ends on the last  Sunday
       in October at 3 AM:

              TZ='CET-1CEST,M3.5.0/2,M10.5.0/3'

       British  time,  daylight  saving  starts and ends at the same moment as
       CET, but in an earlier time zone:

              TZ='GMT0BST,M3.5.0/1,M10.5.0/2'

       The eastern european time zones also have the changeovers at  the  same
       absolute time as British time and CET.

       U.S.  Eastern  Standard  Time,  5  hours  west from Greenwich, daylight
       saving starts on the second Sunday in March at 2 AM  and  ends  on  the
       first Sunday in November at 2 AM:

              TZ='EST5EDT,M3.2.0/2,M11.1.0/2'

       It  shouldn't  surprise  you  that  daylight  saving  in New Zealand is
       observed in the months opposite from the previous examples.  It  starts
       on  the first Sunday in October at 2 AM and ends on the third Sunday in
       March at 3 AM:

              TZ='NZST-12NZDT,M10.1.0/2,M3.3.0/3'

SEE ALSO
       readclock(8), date(1).

BUGS
       You may have noticed that many fields are optional.  Do not omit  them,
       because the defaults are bogus.  If you need daylight saving then fully
       specify the changeovers.

       West is negative, east is positive, ask any sailor.

       Next year's time zone  and  daylight  saving  time  are  determined  by
       politicians.

AUTHOR
       Kees J. Bot (kjb@cs.vu.nl)

                                                                         TZ(5)
NAME | SYNOPSIS | DESCRIPTION | EXAMPLES | SEE ALSO | BUGS | AUTHOR