*nix Documentation Project
·  Home
 +   man pages
·  Linux HOWTOs
·  FreeBSD Tips
·  *niX Forums

  man pages->Linux man pages -> tzset (3)              



NAME    [Toc]    [Back]

       tzset - initialize time conversion information

SYNOPSIS    [Toc]    [Back]

       #include <time.h>

       void tzset (void);

       extern char *tzname[2]

DESCRIPTION    [Toc]    [Back]

       The  tzset() function initializes the tzname variable from the TZ environment
 variable.  This function is automatically called by  the  other
       time conversion functions that depend on the time zone.

       If the TZ variable does not appear in the environment, the tzname variable
 is initialized with the best approximation	of  local  wall  clock
       time,  as specified by the tzfile(5)-format file localtime found in the
       system  timezone  directory  (see  below).   (One   also   often   sees
       /etc/localtime  used  here,  a  symlink to the right file in the system
       timezone directory.)

       If the TZ variable does appear in the environment but its value is NULL
       or  its	value cannot be interpreted using any of the formats specified
       below, Coordinated Universal Time (UTC) is used.

       The value of TZ can be one of three formats.  The first format is  used
       when there is no daylight saving time in the local time zone:

	      std offset

       The std string specifies the name of the time zone and must be three or
       more alphabetic characters.  The offset string immediately follows  std
       and specifies the time value to be added to the local time to get Coordinated
 Universal Time (UTC).  The offset is positive if the local time
       zone  is  west  of  the Prime Meridian and negative if it is east.  The
       hour must be between 0 and 24, and the minutes and seconds 0 and 59.

       The second format is used when there is daylight saving time:

	      std offset dst [offset],start[/time],end[/time]

       There are no spaces in the specification.  The initial std  and	offset
       specify the standard time zone, as described above.  The dst string and
       offset specify the name and offset for the corresponding daylight  savings
  time  zone.   If  the offset is omitted, it defaults  to one hour
       ahead of standard time.

       The start field specifies when daylight savings time goes  into	effect
       and  the  end  field specifies when the change is made back to standard
       time.  These fields may have the following formats:

       Jn     This specifies the Julian day with n between 1 and 365.	February
 29 is never counted even in leap years.

       n      This  specifies the Julian day with n between 1 and 365.	February
 29 is counted in leap years.

       Mm.w.d This specifies day d (0 <= d <= 6) of week w (1 <= w  <=	5)  of
	      month m (1 <= m <= 12).  Week 1 is the first week in which day d
	      occurs and week 5 is the last week in which day d occurs.  Day 0
	      is a Sunday.

       The  time  fields  specify when, in the local time currently in effect,
       the change to the other	time  occurs.	If  omitted,  the  default  is

       The  third  format  specifies  that the time zone information should be
       read from a file:


       If the file specification filespec is omitted, the time	zone  information
  is read from the file localtime in the system timezone directory,
       which  nowadays	usually  is  /usr/share/zoneinfo.   This  file	is  in
       tzfile(5)   format.    If  filespec  is	given,	it  specifies  another
       tzfile(5)-format file to read the time zone information from.  If file-
       spec  does  not begin with a `/', the file specification is relative to
       the system timezone directory.

FILES    [Toc]    [Back]

       The system time zone directory used depends  on	the  (g)libc  version.
       Libc4 and libc5 use /usr/lib/zoneinfo, and, since libc-5.4.6, when this
       doesn't work, will try /usr/share/zoneinfo.  Glibc2 will use the  environment
	variable  TZDIR, when that exists.  Its default depends on how
       it was installed, but normally is /usr/share/zoneinfo.

       This timezone directory contains the files
       localtime      local time zone file
       posixrules     rules for POSIX-style TZ's

       Often /etc/localtime is a symlink to the file localtime or to the  correct
 time zone file in the system time zone directory.

CONFORMING TO    [Toc]    [Back]

       SVID 3, POSIX, BSD 4.3

SEE ALSO    [Toc]    [Back]

       date(1), gettimeofday(2), time(2), ctime(3), getenv(3), tzfile(5)

BSD				  1993-07-02			      TZSET(3)
[ Back ]
 Similar pages
Name OS Title
tzset Tru64 sets and accesses time zone conversion information
timezone Tru64 sets and accesses time zone conversion information
tzname Tru64 sets and accesses time zone conversion information
daylight Tru64 sets and accesses time zone conversion information
inittodr FreeBSD initialize system time
inittodr OpenBSD initialize system time
inittodr NetBSD initialize system time
strptime IRIX date and time conversion
aux IRIX initialize auxiliary identification and authentication information
kkstat HP-UX Kana Kanji Conversion Server information
Copyright © 2004-2005 DeniX Solutions SRL
newsletter delivery service