ultrix man page for tzfile

tzfile(5)							File Formats Manual							 tzfile(5)

Name
       tzfile - time zone information

Syntax
       #include <tzfile.h>

Description
       The time zone information files used by begin with bytes reserved for future use, followed by three 4-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.

		      This header is followed by 4-byte values of type ``long'', sorted in ascending order.  These values are written  in  ``stan-
		      dard''  byte  order.  Each is used as a transition time (as returned by at which the rules for computing local time change).
		      Next come 1-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 structures 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 4-byte value for of type ``long'', in a standard byte order, followed by a 1-byte	value  for
		      and a 1-byte value for In each structure, gives the number of seconds to be added to GMT, tells whether should be set by and
		      serves as an index into the array of time zone abbreviation characters that follows the structure or structures in the file.

       The call uses the first standard-time structure in the file (or simply the first structure, in the absence of a standard-time structure) if
       either is zero or the time argument is less than the first transition time recorded in the file.

See Also
       ctime(3)

																	 tzfile(5)