How to compare Datetime

Hi...

Im having some problems with the datetime fields

Here is an example:
+----------------------------------+----------------------------------+-------+
| Field | Type | Length|
+----------------------------------+----------------------------------+-------+
| id | int4 | 4 |
| fornavn | text | var |
| tilmelddato | datetime | 8 |
+----------------------------------+----------------------------------+-------+

I want to select the entries that came in to the database 15 days ago.
tilmelddato contains the date that the entry was entered.

I do a "select * from testtable where tilmelddato = '01/04/1999'"
but that doesn't return anything even though my database contains
2 entries for that day.

If a do a "select * from testtable where tilmelddato > '01/04/1999'" it
returns 6 hits, but 2 of the hits was entered on the 01/04/1999 and
should not be in there, because of the >.

But if i use the < sign it works as i should. But if i do this:
"Select * from testtable where tilmelddato <= '15/04/1999'" the records
with 15/04/1999 is NOT included in the result set.

Im a bit confused about this .. the = dosnt work, the > and < works
partly

Im running Redhat 5.2 with kernel 2.2.4 and postgresql-6.4.2

Hope someone out there knows the answer :)

With friendly regards

Henrik Pedersen
Denmark