I’m trying to parse some strings into Oracle’s TIMESTAMP WITH TIMEZONE with to_timestamp_tz.

The documentation suggests I should use TZD to parse three-letter codes like PST & PDT. However, that doesn’t seem to work:

SELECT
    to_timestamp_tz('10 Apr 2023 09:09:06 AM UTC', 'DD Mon YYYY HH:MI:SS AM TZD')
FROM
    dual;

ORA-01857: not a valid time zone

I can instead use TZR, which according to the docs should be for region information like US/Pacific:

SELECT
    to_timestamp_tz('10 Apr 2023 09:09:06 AM UTC', 'DD Mon YYYY HH:MI:SS AM TZR')
FROM
    dual;

2023-04-10 09:09:06.000000000 +00:00

TZR handles some three-letter codes but not others, however:

SELECT
    to_timestamp_tz('10 Apr 2023 09:09:06 AM PST', 'DD Mon YYYY HH:MI:SS AM TZR')
FROM
    dual;

2023-04-10 09:09:06.0 PST

SELECT
    to_timestamp_tz('10 Apr 2023 09:09:06 AM PDT', 'DD Mon YYYY HH:MI:SS AM TZR')
FROM
    dual;

ORA-01882: timezone region not found

I can’t figure out the rhyme or reason as to why some of these worksand not others.

I’m using Oracle Database 19c Enterprise Edition Release 19.0.0.0.0 - Production.