Empty Date Field

Hi, could any one tell me how can I tell postgres that a date field I made
in a table can be empty.

I created a table with a field like that but I didn't tell it "not null" in
the declaration, and when I try to fill this table with an empty date it
gives me an error.

Thank you.

Fabian.

______________________________________________________
Get Your Private, Free Email at http://www.hotmail.com