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From: Tom Lane <tgl@sss.pgh.pa.us>
To: marek.lall@eesti.ee
cc: pgsql-bugs@lists.postgresql.org
Subject: Re: BUG #17240: <timestamptz> at time zone ... ; wrong result
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Comments: In-reply-to PG Bug reporting form <noreply@postgresql.org>
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PG Bug reporting form <noreply@postgresql.org> writes:
> # select now()
>  , now() at time zone 'America/Los_Angeles' as correct
>  , now() at time zone '-07:00:00' as wrong;

Unfortunately, the pure-numeric syntax for time zone names follows the
POSIX sign convention, which is opposite to the ISO convention used
in pg_timezone_names.utc_offset (and in most other places in Postgres).
So "at time zone '+07:00:00'" is what you needed to write to duplicate
the 'America/Los_Angeles' result.  See

https://www.postgresql.org/docs/current/datatype-datetime.html#DATATYPE-TI=
MEZONES

Now, if you'd done this:

select ... now() at time zone interval '-07:00:00' as fine

you'd have gotten the ISO sign interpretation.  But an undecorated
literal string defaults to being of type text, meaning you get
the time-zone-name logic path.

The great thing about standards is there are so many to choose from :-(

			regards, tom lane