2007 DST change not working

Another DST related problem in pgsql 8.1.5 ...

drop table dst;
create table dst (tz1 timestamp with time zone, tz2 timestamp with time
zone, tzage interval);
insert into dst ( select ('2005-01-02'::date+(days*7))::timestamptz as t1
from generate_series(0,150) as days );
update dst set tz2 = tz1::timestamp + '12 hours';
update dst set tzage = age( tz2 at time zone 'GMT', tz1 at time zone 'GMT' );
select * from dst where tzage <> '12 hrs';
           tz1           |          tz2           |  tzage
------------------------+------------------------+----------
  2005-04-03 00:00:00-05 | 2005-04-03 12:00:00-04 | 11:00:00
  2005-10-30 00:00:00-04 | 2005-10-30 12:00:00-05 | 13:00:00
  2006-04-02 00:00:00-05 | 2006-04-02 12:00:00-04 | 11:00:00
  2006-10-29 00:00:00-04 | 2006-10-29 12:00:00-05 | 13:00:00
  2007-04-01 00:00:00-05 | 2007-04-01 12:00:00-04 | 11:00:00
  2007-10-28 00:00:00-04 | 2007-10-28 12:00:00-05 | 13:00:00
(6 rows)

My query produces the correct results for 2005 and 2006; but in 2007 DST
dates are changing in North America and my query seems to still be using
2006 rules for 2007 data.  What can I do about this?  Query should report
2007-03-18 and 2007-11-11.

Frank