Using a User-Def function in a query

I've written several user-defined functions (UDFs) for converting
dates to unix time, every which way.
They work find, ala

# select dtu_dmony('22 Sep 2008');
dtu_dmony
------------
1222066800
(1 row)
Returns an integer.

---
Here's a typical query I often run (why I wrote the functions
# select count(distinct username) from stats where eventtime >
1222066800 ;
count
-------
1460
(1 row)

---
but when I try to use the function in a query
# select count(distinct username) from stats where eventtime >
dtu_dmony('22 Sep 2008') ;
it never comes back...

---
Is it the table-like formatting that's killing me?
How do I get around this?

Thanks!

Ralph Smith
smithrn at here washington.edu
=====================