date bug (again)

let me try this again...

Here is an other set of strange bugs I've discovered relating to dates.

this bug only rears it's head for 1 day a year form what I can find..
october 31'st, the intent of the queries is to get the last day of a month..

SELECT date_part('day', ('2000-11-1 0:00'::datetime + '-1day'))::int4 AS
days_in_month;

days_in_month
--------------
31
(1 row)

SELECT date_part('day', (('2000-10-1 0:00'::datetime + '1 month') + '-1
day'))::int4 AS days_in_month;

days_in_month
--------------
30
(1 row)

SELECT date_part('day', date_trunc('month', ('2000-10-1 0:00'::datetime +
'1 month')) + '-1 day')::int4 AS days_in_month;

days_in_month
--------------
30
(1 row)