America/Winnipeg still converts with pre-2026e rules in 17.11.0.x; Manitoba's permanent UTC−5 starts 2026-11-01

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Assessment

Difficulty
4/5
Estimated time
3-5 days
Newbie friendliness
55/100
Issue type
Bug
Clarity
Clearly specified
Activity status
Active
Tech stack
postgresql
Domain
databases

Research direction

The report identifies the embedded timezone data at src/timezone/data/tzdata.zi and reproduces the issue with America/Winnipeg in a SQL query. Start by checking how the image build packages PostgreSQL's timezone data and compare its rules with tzdata 2026e. Done means the reported query returns 2026-11-02 17:00:00+00 and the issue names the image version carrying the update.

Written by the indexing model from the issue text.

Description

bug

Follow-up to #2465, which #2501 closed by moving the build to PostgreSQL's embedded tzdata.

That embedded data is 2026c. IANA tzdata 2026e (released 2026-09-29) moves Manitoba to permanent UTC−5 on
2026-10-31, modelled from 2026-11-01 02:00 local, so every current image still applies the old fall-back to
UTC−6 for America/Winnipeg. (The 2026-10-08 comment on #2465 flagged this class of gap.)

Repro, on any image or project:

select ('2026-11-02 12:00'::timestamp at time zone 'America/Winnipeg')::text;
  • Got: 2026-11-02 18:00:00+00 on public.ecr.aws/supabase/postgres 17.6.1.143, 17.11.0.004 and
    17.11.0.007 (newest tag as of 2026-10-22).
  • Expected with tzdata ≥ 2026e: 2026-11-02 17:00:00+00.

Upgrading to 17.11.0.003 or later, as the 2026-10-09 reply on #2465 suggests, does not fix this: both 17.11 tags
above are later and still answer 18:00.

Impact: from 2026-11-01, every Winnipeg wall-clock time that Postgres converts is an hour off from clients
on current rules (Node ≥ 24.22.1 ships 2026e, and OS and browser updates are rolling out). A scheduling app
computes lesson slots in the database and displays them on the device, so the two disagree by an hour.
PostgreSQL's next minor releases are scheduled for 2026-11-12, after the change.

Ask: ship tzdata 2026e in the images and on hosted projects before 2026-11-01, for example by patching the
embedded src/timezone/data/tzdata.zi or building against a current system tzdata again. Please also say which
image version carries it.

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