The Time Zone Database (often called tz, tzdb, or zoneinfo) contains
data that represents the history of local time for many locations around
the world, and supports conversion of UTC time to local time at those
locations to allow display of those local times. It is updated
periodically to reflect changes made by political bodies to summer
daylight saving time rules, UTC offsets, and time zone boundaries.
Three data packages are now available: base 'tzdata' is always
installed; optional 'tzdata-right' provides TAI-10s time in the 'right'
subtree; and optional 'tzdata-posix' provides the same zones and times
as base data in the 'posix' subtree, as an explicit distinction from
'right'.
The tzcode package provides the tzselect, zdump, and zic utilities.
For more information, see the project home page:
https://www.iana.org/time-zones
The following packages have been upgraded in the Cygwin distribution:
- tzcode 2025a utilities
- tzdata 2025a base zones tree
- tzdata-posix 2025a posix zones subtree
- tzdata-right 2025a TAI-10s right zones subtree
For more details on changes, see the announcement or below:
https://lists.iana.org/hyperkitty/list/[email protected]/2025/1/
2025-01-15 2025a
Briefly:
Paraguay adopts permanent -03 starting spring 2024.
Improve pre-1991 data for the Philippines.
Etc/Unknown is now reserved.
Changes to future timestamps
Paraguay will stop changing its clocks after the spring-forward
transition on 2024-10-06, so it is now permanently at -03.
(Thanks to Heitor David Pinto and Even Scharning.)
This affects timestamps starting 2025-03-22, as well as the
obsolescent tm_isdst flags starting 2024-10-15.
Changes to past timestamps
Correct timestamps for the Philippines before 1900, and from 1937
through 1990. (Thanks to P Chan for the heads-up and citations.)
This includes adjusting local mean time before 1899; fixing
transitions in September 1899, January 1937, and June 1954; adding
transitions in December 1941, November 1945, March and September
1977, and May and July 1990; and removing incorrect transitions in
March and September 1978.
Changes to data
Add zone1970.tab lines for the Concordia and Eyre Bird Observatory
research stations. (Thanks to Derick Rethans and Jule Dabars.)
Changes to documentation
The name Etc/Unknown is now reserved: it will not be used by TZDB.
This is for compatibility with CLDR, which uses the string
"Etc/Unknown" for an unknown or invalid timezone. (Thanks to
Justin Grant, Mark Davis, and Guy Harris.)
Cite Internet RFC 9636, which obsoletes RFC 8536 for TZif format.
Changes to code
strftime %s now generates the correct numeric string even when the
represented number does not fit into time_t. This is better than
generating the numeric equivalent of (time_t) -1, as strftime did
in TZDB releases 96a (when %s was introduced) through 2020a and in
releases 2022b through 2024b. It is also better than failing and
returning 0, as strftime did in releases 2020b through 2022a.
strftime now outputs an invalid conversion specifier as-is,
instead of eliding the leading '%', which confused debugging.
An invalid TZ now generates the time zone abbreviation "-00", not
"UTC", to help the user see that an error has occurred. (Thanks
to Arthur David Olson for suggesting a "wrong result".)
mktime and timeoff no longer incorrectly fail merely because a
struct tm component near INT_MIN or INT_MAX overflows when a
lower-order component carries into it.
TZNAME_MAXIMUM, the maximum number of bytes in a proleptic TZ
string's time zone abbreviation, now defaults to 254 not 255.
This helps reduce the size of internal state from 25480 to 21384
on common platforms. This change should not be a problem, as
nobody uses such long "abbreviations" and the longstanding tzcode
maximum was 16 until release 2023a. For those who prefer no
arbitrary limits, you can now specify TZNAME_MAXIMUM values up to
PTRDIFF_MAX, a limit forced by C anyway; formerly tzcode silently
misbehaved unless TZNAME_MAXIMUM was less than INT_MAX.
tzset and related functions no longer leak a file descriptor if
another thread forks or execs at about the same time and if the
platform has O_CLOFORK and O_CLOEXEC respectively. Also, the
functions no longer let a TZif file become a controlling terminal.
'zdump -' now reads TZif data from /dev/stdin.
(From a question by Arthur David Olson.)
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