now() returning int4

I have a table containing an integer field defaulting to now(), which I
want to use as the unix timestamp counting the seconds from jan 1 1970.
Problem is when I try to perform queries using now():

db=> CREATE TABLE test (
db-> date int default now()
db-> );
CREATE
db=> SELECT * FROM test WHERE date < now();
ERROR:  Unable to identify operator '<' for types 'int4' and 'timestamp'       You will have to retype this query using an explicit cast
db=> SELECT * FROM test WHERE date::timestamp < now();
bis
db=> SELECT * FROM test WHERE date < now()::int4;
bis

Please let me know how I can get this to work properly, I'm using
postgresql 6.5.3.

Marc