Re: Time zone offset in to_char()

On 1/11/24 6:20 PM, Jim Nasby wrote:
> On 1/11/24 5:53 PM, Tom Lane wrote:
>> Adrian Klaver <adrian.klaver@aklaver.com> writes:
>>> test=# select to_char(now() AT TIME ZONE 'Europe/Amsterdam', 'YYYY-MM-DD
>>> HH24:MI:SS.US0 TZH:TZM') ;
>>>                 to_char
>>> ------------------------------------
>>>    2024-01-12 00:44:57.5421420 +00:00
>>> (1 row)
>>
>>> You end up with string that does not the correct offset as the AT TIME
>>> ZONE outputs a timestamp not timestamptz value.
>>
>> Yeah.  to_char() does not have any source for the TZ/TZH/TZM fields
>> other than the prevailing value of the timezone parameter, so you
>> really have to set that the way you want if you desire to use these
>> format fields.  As noted upthread, SET LOCAL together with a (dummy)
>> "SET timezone" clause in the function definition can be used to get
>> the effect of a function-local setting of the parameter.  I don't
>> know of another way to achieve that result above the C-code level.
>>
>>             regards, tom lane
> 
> Sorry, I was implying that you could use the generated timestamp without 
> timezone as a string and supply the necessary timezone:
> 
> select to_char(timestamptz(timezone('UTC',tstz) || ' CST6CDT'), 
> 'YYYY-MM-DD HH24:MI:SS.US0 TZH:TZM') from tstz ;
>                to_char
> ------------------------------------
>   2024-01-11 23:29:00.0493300 -06:00
> (1 row)

NEVERMIND... I see now that doesn't actually work.

Perhaps we should add a variant of timezone() that handles this use-case...
-- 
Jim Nasby, Data Architect, Austin TX