Re: update time zone in timestamps

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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