1 .\" $FreeBSD: src/lib/libc/stdtime/tzfile.5,v 1.8.2.2 2001/08/17 15:42:43 ru Exp $
2 .\" $DragonFly: src/lib/libc/stdtime/tzfile.5,v 1.2 2003/06/17 04:26:46 dillon Exp $
8 .Nd timezone information
10 .Fd #include \&"/usr/src/lib/libc/stdtime/tzfile.h\&"
12 The time zone information files used by
14 begin with the magic characters
17 time zone information files,
18 followed by sixteen bytes reserved for future use,
19 followed by four four-byte values
20 written in a ``standard'' byte order
21 (the high-order byte of the value is written first).
25 .Bl -tag -compact -width tzh_ttisstdcnt
27 The number of UTC/local indicators stored in the file.
29 The number of standard/wall indicators stored in the file.
31 The number of leap seconds for which data is stored in the file.
33 The number of ``transition times'' for which data is stored
36 The number of ``local time types'' for which data is stored
37 in the file (must not be zero).
39 The number of characters of ``time zone abbreviation strings''
43 The above header is followed by
45 four-byte values of type
47 sorted in ascending order.
48 These values are written in ``standard'' byte order.
49 Each is used as a transition time (as returned by
51 at which the rules for computing local time change.
54 one-byte values of type
56 each one tells which of the different types of ``local time'' types
57 described in the file is associated with the same-indexed transition time.
58 These values serve as indices into an array of
60 structures that appears next in the file;
61 these structures are defined as follows:
63 .Bd -literal -offset indent
67 unsigned int tt_abbrind;
71 Each structure is written as a four-byte value for
75 in a standard byte order, followed by a one-byte value for
77 and a one-byte value for
81 gives the number of seconds to be added to UTC,
89 serves as an index into the array of time zone abbreviation characters
92 structure(s) in the file.
96 pairs of four-byte values, written in standard byte order;
97 the first value of each pair gives the time
100 at which a leap second occurs;
103 number of leap seconds to be applied after the given time.
104 The pairs of values are sorted in ascending order by time.
108 standard/wall indicators, each stored as a one-byte value;
109 they tell whether the transition times associated with local time types
110 were specified as standard time or wall clock time,
111 and are used when a time zone file is used in handling POSIX-style
112 time zone environment variables.
116 UTC/local indicators, each stored as a one-byte value;
117 they tell whether the transition times associated with local time types
118 were specified as UTC or local time,
119 and are used when a time zone file is used in handling POSIX-style
120 time zone environment variables.
123 uses the first standard-time
125 structure in the file
128 structure in the absence of a standard-time structure)
131 is zero or the time argument is less than the first transition time recorded
138 .\" This file is in the public domain, so clarified as of
139 .\" 1996-06-05 by Arthur David Olson (arthur_david_olson@nih.gov).