"TZ"/"tz" not supported

Hi,

Execution of the following statement aborts with the error message in
the Subject:

select to_timestamp('2008-06-20 02:30:00 GMT', 'YYYY-MM-DD HH24:MI:SS TZ');

Does this message mean that this particular PostgreSQL installation
doesn't support timezones?

--------------
select * from pg_catalog.pg_timezone_abbrevs where abbrev = 'GMT';
abbrev | utc_offset | is_dst
--------+------------+--------GMT    | 00:00:00   | f
(1 row)
--------------

The database version is 8.3.0.

Any help appreciated,
Peter