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)
