Hi Adrian,
Thanks for your reply. However, I still don't fully understand why
SET TIMEZONE TO and AT TIME ZONE behave differently. Morever the
/usr/share/pgsql/timezonesets/America.txt (POSIX) specifies the BRST timezone
with a two hour negative offset. Unless I'm missing something the AT TIME ZONE
construct is swapping the signs of the offset when specifying the timezone
numerically.
Cheers,
Andrew
-----Original Message-----
From: Adrian Klaver [mailto:[email protected]]
Sent: Friday, 29 January 2010 11:57 AM
To: [email protected]
Cc: Andrew Crouch
Subject: Re: [GENERAL] Behavior of "at time zone"
On Friday 29 January 2010 5:34:04 am Andrew Crouch wrote:
> Hi there,
> I'm looking to use the "at time zone" language feature,
> however the results below don't really agree with my expectations. Is
> this a bug in 8.4 or am I misinterpreting the results? If it is a
> bug, has it been fixed in the development releases?
>
>
> psql (8.4.0)
> Type "help" for help.
>
> ispdb_br=> set timezone to '-2';
> SET
> ispdb_br=> select now();
> now
> -------------------------------
> 2010-01-29 11:26:22.833697-02
> (1 row)
>
> ispdb_br=> select now() at time zone 'BRST';
> timezone
> ----------------------------
> 2010-01-29 11:26:30.521964
> (1 row)
>
> ispdb_br=> select now() at time zone '-2';
> timezone
> ----------------------------
> 2010-01-29 15:26:47.010222
> (1 row)
>
> ispdb_br=> select now() at time zone '+2';
> timezone
> ---------------------------
> 2010-01-29 11:26:49.55412
> (1 row)
From here:
http://www.postgresql.org/docs/8.4/interactive/datatype-datetime.html#DATATYPE-TIMEZONES
"One should be wary that the POSIX-style time zone feature can lead to silently
accepting bogus input, since there is no check on the reasonableness of the
zone abbreviations. For example, SET TIMEZONE TO FOOBAR0 will work, leaving the
system effectively using a rather peculiar abbreviation for UTC. Another issue
to keep in mind is that in POSIX time zone names, positive offsets are used for
locations west of Greenwich. Everywhere else, PostgreSQL follows the ISO-8601
convention that positive timezone offsets are east of Greenwich. "
>
>
> Regards,
> Andrew
--
Adrian Klaver
[email protected]
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