Validity check in to_date?

I just discovered that to_date() function does not check if supplied
date is correct, giving surprising (at least for me) results:

fduch=# SELECT to_date('31.11.2003', 'DD.MM.YYYY');
to_date
------------
2003-12-01

or even

fduch=# SELECT to_date('123.45.2003', 'DD.MM.YYYY');
to_date
------------
2007-01-03

to_timestamp() seems to work the same way. It's probably useful sometimes,
but not in my case... Is it how it supposed to work?
If so, how can I do such a validity check?
If not, has something changed in 7.4?

In any case, I have to find a workaround now and will appreciate any help.

fduch=# SELECT version();
version
---------------------------------------------------------------------
PostgreSQL 7.3.4 on i386-portbld-freebsd4.8, compiled by GCC 2.95.4

--
Fduch M. Pravking