query for records based on date

If I have a table with an attribute of type "timestamp without time
zone", what is the best way to query that table for records that are
older than, say, one week.

I suppose I could get the current time in epoch seconds and the time of
the attribute in the same, and select those records where the difference
is greater than the number of seconds in a week.  Is there something
easier like
 SELECT * FROM table WHERE attribute IS OLDER THAN one week;

Thanks.

-- 
Brandon