1 .\" $FreeBSD: head/contrib/tzcode/stdtime/tzfile.5 259446 2013-12-16 01:58:12Z bjk $
7 .Nd timezone information
11 The time zone information files used by
13 begin with the magic characters
16 time zone information files,
17 followed by a character identifying the version of the file's format
18 (as of 2005, either an ASCII NUL or a '2')
19 followed by fifteen bytes containing zeroes reserved for future use,
20 followed by four four-byte values
21 written in a ``standard'' byte order
22 (the high-order byte of the value is written first).
26 .Bl -tag -compact -width tzh_ttisstdcnt
28 The number of UTC/local indicators stored in the file.
30 The number of standard/wall indicators stored in the file.
32 The number of leap seconds for which data is stored in the file.
34 The number of ``transition times'' for which data is stored
37 The number of ``local time types'' for which data is stored
38 in the file (must not be zero).
40 The number of characters of ``time zone abbreviation strings''
44 The above header is followed by
46 four-byte values of type
48 sorted in ascending order.
49 These values are written in ``standard'' byte order.
50 Each is used as a transition time (as returned by
52 at which the rules for computing local time change.
55 one-byte values of type
57 each one tells which of the different types of ``local time'' types
58 described in the file is associated with the same-indexed transition time.
59 These values serve as indices into an array of
63 entries) that appears next in the file;
64 these structures are defined as follows:
66 .Bd -literal -offset indent
70 unsigned int tt_abbrind;
74 Each structure is written as a four-byte value for
78 in a standard byte order, followed by a one-byte value for
80 and a one-byte value for
84 gives the number of seconds to be added to UTC,
92 serves as an index into the array of time zone abbreviation characters
95 structure(s) in the file.
99 pairs of four-byte values, written in standard byte order;
100 the first value of each pair gives the time
103 at which a leap second occurs;
106 number of leap seconds to be applied after the given time.
107 The pairs of values are sorted in ascending order by time.
111 standard/wall indicators, each stored as a one-byte value;
112 they tell whether the transition times associated with local time types
113 were specified as standard time or wall clock time,
114 and are used when a time zone file is used in handling POSIX-style
115 time zone environment variables.
119 UTC/local indicators, each stored as a one-byte value;
120 they tell whether the transition times associated with local time types
121 were specified as UTC or local time,
122 and are used when a time zone file is used in handling POSIX-style
123 time zone environment variables.
126 uses the first standard-time
128 structure in the file
131 structure in the absence of a standard-time structure)
134 is zero or the time argument is less than the first transition time recorded
137 For version-2-format time zone files,
138 the above header and data is followed by a second header and data,
139 identical in format except that eight bytes are used for each
140 transition time or leap second time.
141 After the second header and data comes a newline-enclosed,
142 POSIX-TZ-environment-variable-style string for use in handling instants
143 after the last transition time stored in the file
144 (with nothing between the newlines if there is no POSIX representation for
151 .\" This file is in the public domain, so clarified as of
152 .\" 1996-06-05 by Arthur David Olson.