Re: Timestamp with timezone question.

On 2005-02-21, Achilleus Mantzios <achill(at)matrix(dot)gatewaynet(dot)com> wrote:
> Consider a schema designed to store internet mail.
>
> Since pgsql always converts a timestamptz to UTC, we have lost
> the information of the Sender's local timezone.
>
> Should i go with a separete date and timetz ?

No. Consider instead storing a timestamptz with the actual time of the
mail, and a separate field with an interval representing the zone offset.
Then you can use AT TIME ZONE to recover the sender's local time.

e.g. (this table has columns serial, timestamptz, interval)

insert into dtz values (DEFAULT,
'2005-03-21 07:05:00 -0800',
'2005-03-21 07:05:00 -0800'::timestamp
- '2005-03-21 07:05:00 -0800'::timestamptz at time zone 'UTC'
);

(the timestamp - timestamptz thing is just a reasonably reliable way of
getting the timezone offset without complicated parsing.)

select * from dtz;
id | t | z
----+------------------------+-----------
1 | 2005-03-21 15:05:00+00 | -08:00:00
(1 row)

select *, t at time zone z as ot from dtz;
id | t | z | ot
----+------------------------+-----------+---------------------
1 | 2005-03-21 15:05:00+00 | -08:00:00 | 2005-03-21 07:05:00
(1 row)

--
Andrew, Supernews
http://www.supernews.com - individual and corporate NNTP services