Re: Timezone database changes

From: Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us>
To: "Trevor Talbot" <quension(at)gmail(dot)com>
Cc: "Aidan Van Dyk" <aidan(at)highrise(dot)ca>, "Peter Eisentraut" <peter_e(at)gmx(dot)net>, pgsql-hackers(at)postgresql(dot)org, Magne Mæhre <Magne(dot)Mahre(at)sun(dot)com>
Subject: Re: Timezone database changes
Date: 2007-10-10 16:43:17
Message-ID: 18765.1192034597@sss.pgh.pa.us
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"Trevor Talbot" <quension(at)gmail(dot)com> writes:
> Actually, what I meant at least (not sure if others meant it), is
> storing the value in the timezone it was entered, along with what zone
> that was. That makes the value stable with respect to the zone it
> belongs to, instead of being stable with respect to UTC. When DST
> rules change, the value is in effect "reinterpreted" as if it were
> input using the new rules.

What happens if the rules change in a way that makes the value illegal
or ambiguous (ie, it now falls into a DST gap)?

But perhaps more to the point, please show use-cases demonstrating that
this behavior is more useful than the pure-UTC behavior. For storage of
actual time observations, I think pure-UTC is unquestionably the more
useful. Peter's example of a future appointment time is a possible
counterexample, but as observed upthread it's hardly clear which
behavior is more desirable in such a case.

regards, tom lane

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