2.11BSD#431 - /usr/man/cat5/tzfile.0

TZFILE(5)	    UNIX Programmer's Manual		TZFILE(5)


NAME
     tzfile - time zone information

SYNOPSIS
     #include <tzfile.h>

DESCRIPTION
     The time zone information files used by tzset(3) begin with
     bytes reserved for future use, followed by three four-byte
     values of type long, written in a ``standard'' byte order
     (the high-order byte of the value is written first).  These
     values are, in order:

     tzh_timecnt
	  The number of "transition times" for which data is
	  stored in the file.

     tzh_typecnt
	  The number of "local time types" for which data is
	  stored in the file (must not be zero).

     tzh_charcnt
	  The number of characters of "time zone abbreviation
	  strings" stored in the file.

     The above header is followed by tzh_timecnt four-byte values
     of type long, sorted in ascending order.  These values are
     written in ``standard'' byte order.  Each is used as a tran-
     sition time (as returned by time(2)) at which the rules for
     computing local time change.  Next come tzh_timecnt one-byte
     values of type unsigned char; each one tells which of the
     different types of ``local time'' types described in the
     file is associated with the same-indexed transition time.
     These values serve as indices into an array of ttinfo struc-
     tures that appears next in the file; these structures are
     defined as follows:

	  struct ttinfo {
	       long	     tt_gmtoff;
	       int	     tt_isdst;
	       unsigned int  tt_abbrind;
	  };

     Each structure is written as a four-byte value for tt_gmtoff
     of type long, in a standard byte order, followed by a one-
     byte value for tt_isdst and a one-byte value for tt_abbrind.
     In each structure, tt_gmtoff gives the number of seconds to
     be added to GMT, tt_isdst tells whether tm_isdst should be
     set by localtime (3) and tt_abbrind serves as an index into
     the array of time zone abbreviation characters that follow
     the ttinfo structure(s) in the file.


Printed 11/26/99						1


TZFILE(5)	    UNIX Programmer's Manual		TZFILE(5)


     Localtime uses the first standard-time ttinfo structure in
     the file (or simply the first ttinfo structure in the
     absence of a standard-time structure) if either tzh_timecnt
     is zero or the time argument is less than the first transi-
     tion time recorded in the file.

SEE ALSO
     ctime(3)


Printed 11/26/99						2