[DISCUSS] Backport tzdata updates to REL_2_STABLE to fix Mexico timezone issue

[Max Yang <ma...@gmail.com>]

Hi all,

I'd like to bring up a timezone data issue that was recently reported
by a community user and share what we've found so far.

A user in Mexico reported a 1-hour time discrepancy between the OS
and the database when using the America/Mexico_City timezone. After
investigation, we identified the root cause:

1. Mexico abolished Daylight Saving Time in October 2022

Mexico officially stopped observing DST, so America/Mexico_City
should now stay on CST (UTC-6) year-round. However, the database
still switches to CDT (UTC-5) every April, causing the 1-hour
discrepancy the user reported.

2. Cloudberry's bundled tzdata is outdated

Cloudberry is based on PostgreSQL 14.4 (circa 2022), which ships
with tzdata 2022a (released March 2022) — before Mexico's DST
abolishment was enacted. The fix was included in tzdata 2022f
(released October 2022), but Cloudberry never picked it up.

3. PostgreSQL upstream has long since fixed this

Upstream PostgreSQL updated the bundled tzdata multiple times since
then, with the latest being 2025b. The key change was modifying
the Mexico DST rule from "2002 to max" to "2002 to 2022", so that
DST is no longer applied after 2022.

I have verified that the upstream tzdata updates (2022f through
2025b) can be cleanly cherry-picked onto the REL_2_STABLE branch.
A draft PR is available at:

https://github.com/apache/cloudberry/pull/1674

The changes are limited to timezone data files only — no code logic
is involved. Besides the Mexico fix, these updates also include DST
law changes for Greenland and Chile, new timezones like
America/Ciudad_Juarez and America/Coyhaique, and historical
corrections for multiple regions.

We don't need to apply this to main separately, as it will be
covered by the upcoming PostgreSQL 16.x merge.

The original issue is tracked at:

https://github.com/apache/cloudberry/issues/1670

Any feedback or concerns are welcome. Thanks!

Best regards, Max Yang

Re: [DISCUSS] Backport tzdata updates to REL_2_STABLE to fix Mexico timezone issue

[Max Yang <ma...@gmail.com>]

Hi all,

Quick update on this — the PR has been merged:

https://github.com/apache/cloudberry/pull/1674
The bundled timezone data on REL_2_STABLE is now updated to tzdata
2025b. This includes the fix for America/Mexico_City (Mexico DST
abolishment) along with all other upstream timezone changes through
2025b.

The issue has been closed:

https://github.com/apache/cloudberry/issues/1670
Thanks to everyone who reviewed!

Best regards, Max Yang


On Fri, Apr 10, 2026 at 10:17 AM Max Yang <ma...@gmail.com> wrote:

> Hi all,
>
> I'd like to bring up a timezone data issue that was recently reported
> by a community user and share what we've found so far.
>
> A user in Mexico reported a 1-hour time discrepancy between the OS
> and the database when using the America/Mexico_City timezone. After
> investigation, we identified the root cause:
>
> 1. Mexico abolished Daylight Saving Time in October 2022
>
> Mexico officially stopped observing DST, so America/Mexico_City
> should now stay on CST (UTC-6) year-round. However, the database
> still switches to CDT (UTC-5) every April, causing the 1-hour
> discrepancy the user reported.
>
> 2. Cloudberry's bundled tzdata is outdated
>
> Cloudberry is based on PostgreSQL 14.4 (circa 2022), which ships
> with tzdata 2022a (released March 2022) — before Mexico's DST
> abolishment was enacted. The fix was included in tzdata 2022f
> (released October 2022), but Cloudberry never picked it up.
>
> 3. PostgreSQL upstream has long since fixed this
>
> Upstream PostgreSQL updated the bundled tzdata multiple times since
> then, with the latest being 2025b. The key change was modifying
> the Mexico DST rule from "2002 to max" to "2002 to 2022", so that
> DST is no longer applied after 2022.
>
> I have verified that the upstream tzdata updates (2022f through
> 2025b) can be cleanly cherry-picked onto the REL_2_STABLE branch.
> A draft PR is available at:
>
> https://github.com/apache/cloudberry/pull/1674
>
> The changes are limited to timezone data files only — no code logic
> is involved. Besides the Mexico fix, these updates also include DST
> law changes for Greenland and Chile, new timezones like
> America/Ciudad_Juarez and America/Coyhaique, and historical
> corrections for multiple regions.
>
> We don't need to apply this to main separately, as it will be
> covered by the upcoming PostgreSQL 16.x merge.
>
> The original issue is tracked at:
>
> https://github.com/apache/cloudberry/issues/1670
>
> Any feedback or concerns are welcome. Thanks!
>
> Best regards, Max Yang
>