From: Tom Lane <tgl@sss.pgh.pa.us>
To: Andrew Gierth <andrew@tao11.riddles.org.uk>
cc: 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.)
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Comments: In-reply-to Andrew Gierth <andrew@tao11.riddles.org.uk>
	message dated "Fri, 14 Jun 2019 19:24:50 +0100"
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Date: Fri, 14 Jun 2019 15:12:16 -0400
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Andrew Gierth <andrew@tao11.riddles.org.uk> writes:
> This isn't good enough, because it still picks "UCT" on a system with no
> /etc/localtime and no TZ variable. Testing on HEAD as of 3da73d683 (on
> FreeBSD, but it'll be the same anywhere else):

[ shrug... ]  Too bad.  I doubt that that's a common situation anyway.

> We need to absolutely prefer UTC over UCT if both match.

I don't see a reason why that's a hard requirement.  There are at least
two ways for a user to override initdb's decision (/etc/localtime or TZ),
or she could just change the GUC setting after the fact, and for that
matter it's not obvious that it matters to most people how TimeZone
is spelled as long as it delivers the right external behavior.  We had
the business with "Navajo" being preferred for US Mountain time for
quite a few years, with not very many complaints.

I don't see any way that we could "fix" this except with a hardwired
special case to prefer UTC over other spellings, and I definitely do
not want to go there.  If we start putting in magic special cases to make
particular zone names be preferred over other ones, where will we stop?
(I've been lurking on the tzdb mailing list for long enough now to know
that that's a fine recipe for opening ourselves up to politically-
motivated demands that name X be preferred over name Y.)

A possibly better idea is to push back on tzdb's choice to unify
these zones.   Don't know if they'd listen, but we could try.  The
UCT symlink hasn't been out there so long that it's got much inertia.

			regards, tom lane