Re: update time zone in timestamps

From: CSN <cool_screen_name90001(at)yahoo(dot)com>
To: pgsql-general(at)postgresql(dot)org
Subject: Re: update time zone in timestamps
Date: 2003-12-05 23:40:59
Message-ID: 20031205234059.6865.qmail@web40613.mail.yahoo.com
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SHOW ALL shows TimeZone is 'unknown'. postgres.conf
says 'TZ' is used for default. Where should TZ be set
(it doesn't appear to be set on my RH9 system)?

Thanks,
CSN

--- CSN <cool_screen_name90001(at)yahoo(dot)com> wrote:
>
> Does Postgres use the system's timezone
> (/etc/localzone) at all? Or does "SET TIME ZONE
> 'MST'"
> need to be placed in postgres.conf to make it always
> used (I set it via psql, but it appears to only be
> set
> for that connection)?
>
> Thanks,
> CSN
>
>
> --- Tom Lane <tgl(at)sss(dot)pgh(dot)pa(dot)us> wrote:
> > CSN <cool_screen_name90001(at)yahoo(dot)com> writes:
> > > Is it possible to update the timezone part of
> > > timestamp fields in a single query? I have a
> bunch
> > of
> > > values that are -06 I need changed to -07.
> >
> > I suspect that you have a fundamental conceptual
> > error.
> >
> > You cannot "update the timezone" because the
> > timezone is not part of the
> > stored value; it is part of the display operation.
>
> > Stored values for
> > timestamptz columns are always effectively in UTC.
>
> > When the value is
> > converted to a string for display, it is adjusted
> to
> > your current local
> > timezone (per SET TIME ZONE) and that timezone is
> > what's put on the
> > output.
> >
> > So the basic answer is you don't change the data,
> > you change your
> > TIME ZONE setting from -6 to -7 if that's what you
> > want to see.
> >
> > You might have an additional problem that the data
> > was entered
> > incorrectly, and is one hour off from reality
> > because you were
> > confused about time zones when you put it in. In
> > that case you'd
> > fix it with something like
> > UPDATE tab SET col = col + '1 hour'::interval;
> >
> > regards, tom lane
>
>
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