text: -- timestamp -> timestamptz
  CREATE OR REPLACE FUNCTION csm_local_timestamp(timestamp = clock_timestamp())
      RETURNS timestamptz
      LANGUAGE sql
      STABLE
  AS $BODY$
      SELECT timezone('America/Los_Angeles', $1);
  $BODY$;
  
  -- timestamptz -> timestamp
  CREATE OR REPLACE FUNCTION csm_local_timestamp(timestamptz = clock_timestamp())
      RETURNS timestamp
      LANGUAGE sql
      STABLE
  AS $BODY$
      SELECT timezone('America/Los_Angeles', $1);
  $BODY$;