As an intermediate step, it's converting the time back to your local time zone. Try this instead:
openacs4=# select to_char(now(),'yyyy-mm-dd hh24:mi') at time zone 'utc';
timezone
------------------------
2001-04-12 11:48:00+00
(1 row)
openacs4=# select now() at time zone 'utc';
timezone
------------------------
2001-04-12 11:48:12+00
(1 row)
openacs4=# select now();
now
------------------------
2001-04-12 07:50:26-04
(1 row)