Updated: tzdata/-posix/-right, tzcode 2026b - Time Zone Database and Utilities

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 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'.

To enable newlib CLOCK_TAI support, the base tzdata package now installs:

	/usr/share/zoneinfo/leap-seconds.list

with a symbolic link from the standard location:

	/etc/leap-seconds.list.

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	2026b	utilities
- tzdata	2026b	base zones tree
- tzdata-posix	2026b	posix zones subtree
- tzdata-right	2026b	TAI-10s right zones subtree

For more details on changes, see the announcement or below:

	https://lists.iana.org/hyperkitty/list/[email protected]/2026/04/


2026-04-22	2026b

Briefly:

- British Columbia moved to permanent -07 on 2026-03-09.

- Some more overflow bugs have been fixed in zic.

Changes to future timestamps

- British Columbia's 2026-03-08 spring forward was its last foreseeable
  clock change, as it moved to permanent -07 thereafter.
  Although the change to permanent -07 legally took place on 2026-03-09,
  temporarily model the change to occur on 2026-11-01 at 02:00 instead.
  This works around a limitation in CLDR v48.2 (2026-03-17).
  This temporary hack is planned to be removed after CLDR is fixed.

Changes to code

- zic no longer mishandles a last transition to a new time type.

- zic no longer overflows a buffer when generating a TZ string like
  "PST-167:59:58PDT-167:59:59,M11.5.6/-167:59:59,M12.5.6/-167:59:59",
  which can occur with adversarial input.

- zic no longer generates a longer TZif file than necessary when an
  earlier time zone abbreviation is a suffix of a later one.
  As a nice side effect, zic no longer overflows a buffer when given a
  long series of abbreviations, each a suffix of the next.

- zic no longer overflows an int when processing input like
  "Zone Ouch 2147483648:00:00 - LMT".
  The int overflow can lead to buffer overflow in adversarial cases.

- zic now checks for signals more often.

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