Re: Returning timestamp with timezone at specified timezone irrespective of client timezone

On 9/27/20 4:16 PM, aNullValue (Drew Stemen) wrote:

Hello,

I've attempted to obtain help with this problem from several other places, but numerous individuals recommended I ask this mailing list.

What I need is for the ability to return a timestamp with timezone, using the UTC offset that corresponds to a column-defined timezone, irrespective of the client/session configured timezone.

I have three columns in a table:

Timezone: 'US/Eastern'

Date: 2020-10-31

Time: 08:00

The output I'm able to find includes these possibilities:

'2020-10-31 08:00:00'

'2020-10-31 12:00:00+00'

Whereas what I actually need is:

'2020-10-31 08:00:00-05'

Using the postgresql session-level timezone configuration won't work because I need multiple timezones to be handled in a single set.

Example code follows. I'm not using to_char in the examples as I likely would in the production code, but I haven't found any way that it could be helpful here regardless.

[snip]

id |  timezone  |  loc_date  | loc_time |         tswtz          |       tswotz

----+------------+------------+----------+------------------------+---------------------

  7 | US/Central | 2020-10-31 | 08:00    | 2020-10-31 13:00:00+00 | 2020-10-31 08:00:00

  8 | US/Central | 2020-11-03 | 08:00    | 2020-11-03 14:00:00+00 | 2020-11-03 08:00:00

  5 | US/Eastern | 2020-10-31 | 08:00    | 2020-10-31 12:00:00+00 | 2020-10-31 08:00:00

  6 | US/Eastern | 2020-11-03 | 08:00    | 2020-11-03 13:00:00+00 | 2020-11-03 08:00:00

(4 rows)

What I actually need is, in example id=7, '2020-10-31 08:00:00-05'.

Is this even possible? Several people have proposed that I write a custom function to do this on a per-row basis, which... I suppose I can do... I'm just blown away that this isn't something that just works "out of the box".

Are you really asking what the TZ offset was on a specific date (Like DST or not)?

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