2 .\" This file is in the public domain, so clarified as of
3 .\" 1996-06-05 by Arthur David Olson <arthur_david_olson@nih.gov>.
4 .TH TZFILE 5 1996-06-05 "" "Linux Programmer's Manual"
6 tzfile \- timezone information
10 The timezone information files used by
12 begin with the magic characters "TZif" to identify then as
13 timezone information files,
14 followed by sixteen bytes reserved for future use,
15 followed by six four-byte values of type
17 written in a "standard" byte order
18 (the high-order byte of the value is written first).
23 The number of UTC/local indicators stored in the file.
26 The number of standard/wall indicators stored in the file.
29 The number of leap seconds for which data is stored in the file.
32 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).
40 The number of characters of "timezone 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:
68 unsigned int tt_abbrind;
73 Each structure is written as a four-byte value for
77 in a standard byte order, followed by a one-byte value for
79 and a one-byte value for
83 gives the number of seconds to be added to UTC,
91 serves as an index into the array of timezone abbreviation characters
94 structure(s) in the file.
98 pairs of four-byte values, written in standard byte order;
99 the first value of each pair gives the time
102 at which a leap second occurs;
105 number of leap seconds to be applied after the given time.
106 The pairs of values are sorted in ascending order by time.
110 standard/wall indicators, each stored as a one-byte value;
111 they tell whether the transition times associated with local time types
112 were specified as standard time or wall clock time,
113 and are used when a timezone file is used in handling POSIX-style
114 timezone environment variables.
118 UTC/local indicators, each stored as a one-byte value;
119 they tell whether the transition times associated with local time types
120 were specified as UTC or local time,
121 and are used when a timezone file is used in handling POSIX-style
122 timezone environment variables.
125 uses the first standard-time
127 structure in the file
130 structure in the absence of a standard-time structure)
133 is zero or the time argument is less than the first transition time recorded