Another point here is that we have always accepted single digits in dates:
portal=> select '2008-11-1'::date;
date
------------
2008-11-01
(1 row)
portal=> select '2008-1-11'::date;
date
------------
2008-01-11
(1 row)
If we're going to handle dates and timestamps inconsistently, there
should be a good reason for it.
...Robert