deps(deps): Bump tzdata from 2026.3 to 2026.4

[dependabot]

Bumps tzdata from 2026.3 to 2026.4.

Release notes

Sourced from tzdata's releases.

2026.4: Release of upstream tzdata 2026d

Version 2026.4

Upstream version 2026d released 2026-09-11T22:21:07+00:00

Briefly:

Canada’s Northwest Territories moved to permanent -06 on 2026-08-21. Obsolescent settings like TZ="EST5EDT" now conform better to POSIX. Fix security, performance and porting bugs in zic and localtime.

Changes to future timestamps

Canada’s Northwest Territories will not fall back on 2026-11-01 and will stay on -06 year-round, matching Alberta’s recent change. Model this with its traditional abbreviation CST. Although the change to permanent -06 legally took place on 2026-08-21, temporarily model the change to occur on 2026-11-01 at 02:00 for the same reason as other recent temporary hacks. (Caution: see “NOTE FOR 2026b TEMPORARY HACK FOR CLDR AND CANADA” below.) This affects only America/Inuvik as the rest of the territory is covered by America/Edmonton, for which the equivalent change was released in 2026c.

Changes to past timestamps

Colombia’s 1992-05-02 spring forward was at 00:00, not 24:00.

Iran’s 1979-05-26 spring forward was at 00:00, not 24:00. (Thanks to N.F. Hase.)

The backward-compatibility names EST5EDT, CST6CDT, MST7MDT, and PST8PDT now conform better to POSIX. For example, EST5EDT now always uses the abbreviation "EST" for standard time (now always 5 hours behind UT) and "EDT" for daylight saving time, whereas it formerly had different UT offsets before standard time was introduced and sometimes used abbreviations like "LMT", "EWT" and "EPT", all contrary to POSIX. Also, though not required by POSIX these names now use US federal rules rather than rules of places like New York, reverting to 2024a behavior. This change affects only timestamps before 1966-10-30 at 01:00 standard time.

Other data changes

The temporary hacks used for North American timekeeping changes now work around a libstdc++ std::chrono bug in GCC 14.1-14.4, 15.1-15.2, and 16.1; see GCC bug 124851. This data change does not affect TZif files or timestamps. The change does not work around the related but less serious GCC bugs 116110 and 124513. These GCC bugs are all fixed in GCC 16.2.

Changes to documentation

URLs for release tarballs in tz-link.html have been updated to reflect their new canonical URLs on data.iana.org.

Changelog

Sourced from tzdata's changelog.

Version 2026.4

Upstream version 2026d released 2026-09-11T22:21:07+00:00

Briefly:

Canada’s Northwest Territories moved to permanent -06 on 2026-08-21. Obsolescent settings like TZ="EST5EDT" now conform better to POSIX. Fix security, performance and porting bugs in zic and localtime.

Changes to future timestamps

Canada’s Northwest Territories will not fall back on 2026-11-01 and will stay on -06 year-round, matching Alberta’s recent change. Model this with its traditional abbreviation CST. Although the change to permanent -06 legally took place on 2026-08-21, temporarily model the change to occur on 2026-11-01 at 02:00 for the same reason as other recent temporary hacks. (Caution: see “NOTE FOR 2026b TEMPORARY HACK FOR CLDR AND CANADA” below.) This affects only America/Inuvik as the rest of the territory is covered by America/Edmonton, for which the equivalent change was released in 2026c.

Changes to past timestamps

Colombia’s 1992-05-02 spring forward was at 00:00, not 24:00.

Iran’s 1979-05-26 spring forward was at 00:00, not 24:00. (Thanks to N.F. Hase.)

The backward-compatibility names EST5EDT, CST6CDT, MST7MDT, and PST8PDT now conform better to POSIX. For example, EST5EDT now always uses the abbreviation "EST" for standard time (now always 5 hours behind UT) and "EDT" for daylight saving time, whereas it formerly had different UT offsets before standard time was introduced and sometimes used abbreviations like "LMT", "EWT" and "EPT", all contrary to POSIX. Also, though not required by POSIX these names now use US federal rules rather than rules of places like New York, reverting to 2024a behavior. This change affects only timestamps before 1966-10-30 at 01:00 standard time.

Other data changes

The temporary hacks used for North American timekeeping changes now work around a libstdc++ std::chrono bug in GCC 14.1-14.4, 15.1-15.2, and 16.1; see GCC bug 124851. This data change does not affect TZif files or timestamps. The change does not work around the related but less serious GCC bugs 116110 and 124513. These GCC bugs are all fixed in GCC 16.2.

Changes to documentation

URLs for release tarballs in tz-link.html have been updated to reflect their new canonical URLs on data.iana.org.

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Commits

• b4d2086 Update tzdata to version 2026d (#153)
• 91a9022 Switch keyserver used for tarball GPG verification (#152)
• c97164f Bump the actions group with 3 updates (#150)
• 6c7fa78 Stop testing 3.8 and 3.9, test 3.15 and PyPy3 (#148)
• d165386 Bump the Actions group with 2 updates (#149)
• See full diff in compare view

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[VortexUK]

Landed on main in 5d03528 (batched with the other dependabot bumps).

[dependabot]

OK, I won't notify you again about this release, but will get in touch when a new version is available. If you'd rather skip all updates until the next major or minor version, let me know by commenting @dependabot ignore this major version or @dependabot ignore this minor version. You can also ignore all major, minor, or patch releases for a dependency by adding an ignore condition with the desired update_types to your config file.

If you change your mind, just re-open this PR and I'll resolve any conflicts on it.