Despite the name, TIMESTAMP WITH TIME ZONE
doesn't actually store the time zone. It uses the session's time zone to normalize to UTC, and stores UTC. On retrieval it converts back from UTC to the session time zone.
You can change the session time zone by using the SET TIME ZONE
command. Preferably, you should use the standard IANA time zone identifiers. For example:
SET TIME ZONE 'Europe/Paris'
or
SET TIME ZONE 'UTC'
Alternatively use the TIMESTAMP [WITHOUT TIME ZONE]
type instead, which does no conversions.