Re: [PATCH] initdb: map Windows' new Canadian time zone names

On Tue, 20 Oct 2026 at 15:45, Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us> wrote:
>
> David Rowley <dgrowleyml(at)gmail(dot)com> writes:
> > Assume that's what you meant?
>
> No, I was a bit mystified by these printouts:
>
> Timezone Central Asia Standard Time changed displayname ('(UTC+06:00) Bishkek' from '(UTC+06:00) Astana')!
> Timezone Greenland Standard Time changed displayname ('(UTC-02:00) Greenland' from '(UTC-03:00) Greenland')!
> Timezone Greenwich Standard Time changed displayname ('(UTC+00:00) Monrovia, Reykjavik' from 'Windows uses this zone name in various places that lie near the prime meridian, but are not in the UK. However, most people probably think that "Greenwich" means UK civil time, or maybe even straight-up UTC. Atlantic/Reykjavik is a decent match for that interpretation because Iceland hasn't observed DST since 1968. / / (UTC+00:00) Monrovia, Reykjavik')!
> Timezone Jerusalem Standard Time changed displayname ('(UTC+02:00) Jerusalem' from '(UTC+02:00) Jerusalem (old spelling of zone name)')!
> Timezone Jordan Standard Time changed displayname ('(UTC+03:00) Amman' from '(UTC+02:00) Amman')!
> Timezone Morocco Standard Time changed displayname ('(UTC+00:00) Casablanca' from '(UTC+01:00) Casablanca')!
> Timezone Mountain Standard Time (Mexico) changed displayname ('(UTC-07:00) La Paz, Mazatlan' from '(UTC-07:00) Chihuahua, La Paz, Mazatlan')!
> Timezone Paraguay Standard Time changed displayname ('(UTC-03:00) Asuncion' from '(UTC-04:00) Asuncion')!
> Timezone Qyzylorda Standard Time changed displayname ('(UTC+05:00) Astana' from '(UTC+05:00) Qyzylorda')!
> Timezone Syria Standard Time changed displayname ('(UTC+03:00) Damascus' from '(UTC+02:00) Damascus')!
> Timezone Volgograd Standard Time changed displayname ('(UTC+03:00) Volgograd' from '(UTC+04:00) Volgograd')!

They're variations from what's in findtimezone.c and the corresponding
Windows registry key.

> The report for Greenwich Standard Time is probably explainable by our
> having this commentary in findtimezone.c:
>
> /*
> * Windows uses this zone name in various places that lie near the
> * prime meridian, but are not in the UK. However, most people
> * probably think that "Greenwich" means UK civil time, or maybe even
> * straight-up UTC. Atlantic/Reykjavik is a decent match for that
> * interpretation because Iceland hasn't observed DST since 1968.
> */
> /* (UTC+00:00) Monrovia, Reykjavik */

Yeah, the regex in win32tzlist.pl must be merging the comments. I
guess we could adjust that to only look at the last block comment.

> and the Jerusalem report also visibly traces to our own commentary.
> But the ones where the claimed UTC offset changes don't appear to me
> to match up to anything.

I didn't look at all, but did check Europe/Volgograd, and I'm not an
expert at reading tzdata.zi, but doesn't the following mean they
changed to UTC+3 in 2020?

4 - %z 2020 D 27 2s
3 - MSK

If so, isn't Microsoft's "(UTC+03:00) Volgograd" correct here?

The 2020 change seems to be mentioned in [1].

David

[1] https://www.timeanddate.com/time/zone/russia/volgograd?year=2020