TZFILE(5) File Formats Manual TZFILE(5)

NAME

tzfiletime zone information

DESCRIPTION

The time zone information files used by tzset(3) are typically found under a directory with a name like /usr/share/zoneinfo. These files beging with a 44-byte header containing the following fields:

Version 2 format

For version-2-format time zone files, the above header and data are followed by a second header and data, identical in format except that eight bytes are used for each transition time or leap second time. (Leap second counts remain four bytes.) After the second header and data comes a newline-enclosed, POSIX-TZ-environment-variable-style string for use in handling instants after the last transition time stored in the file (with nothing between the newlines if there is no POSIX representation for such instants). The POSIX-style string must agree with the local time type after both data's last transition times; for example, given the string “WET0WEST,M3.5.0,M10.5.0/3” then if a last transition time is in July, the transition's local time type must specify a daylight-saving time abbreviated “WEST” that is one hour east of UT.

Version 3 format

For version-3-format time zone files, the POSIX-TZ-style string may use two minor extensions to the POSIX TZ format, as described in tzset(3). First, the hours part of its transition times may be signed and range from -167 through 167 instead of the POSIX-required unsigned values from 0 through 24. Second, DST is in effect all year if it starts January 1 at 00:00 and ends December 31 at 24:00 plus the difference between daylight saving and standard time.
Future changes to the format may append more data.

SEE ALSO

ctime(3), localtime(3), time(3), tzset(3), zdump(8) zic(8)
October 6, 2016 NetBSD 8.99