From: Tom Lane <tgl@sss.pgh.pa.us>
To: Andres Freund <andres@anarazel.de>
cc: Andrew Gierth <andrew@tao11.riddles.org.uk>,
        Christoph Berg <myon@debian.org>,
        PostgreSQL Hackers <pgsql-hackers@postgresql.org>
Subject: Re: UCT (Re: pgsql: Update time zone data files to tzdata release
 2019a.)
In-reply-to: <20190606171850.ilssehzrvrrfuiqs@alap3.anarazel.de>
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Comments: In-reply-to Andres Freund <andres@anarazel.de>
	message dated "Thu, 06 Jun 2019 10:18:50 -0700"
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Date: Thu, 06 Jun 2019 13:44:54 -0400
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Andres Freund <andres@anarazel.de> writes:
> On 2019-06-06 12:51:30 -0400, Tom Lane wrote:
>> Sure, that is intentionally a behavior change in this situation.
>> The theory is that if "Etc/UCT" is what the user put in /etc/localtime,
>> then that's the spelling she wants.  See 23bd3cec6.

> Right, I'm not complaining about that. I'm just noting that that
> explains the cross-version divergence.

It explains some cross-version divergence for sure.  What I'm still not
clear about is whether Christoph's report is entirely that, or whether
there's some additional factor we don't understand yet.

> As you can see the switch from Etc/UTC to UCT does happen here
> (presumably in any branch before 12). Which did not happen before the
> import of 2019a / when using a system tzdata that's before
> that.

Right.  Before 2019a, UCT would not have been a match to a system
setting of UTC because the zone abbreviation reported by localtime()
was different.  Now it's the same abbreviation.

Maybe we should consider back-patching 23bd3cec6.

			regards, tom lane