[Zope] Blank Date Field?

Is there some easy way to allow for the storage and display of an empty/blank date field? It seems that you are unable to enter a blank value if you defined a property field as storing a date value. I want to be able to store dates in my object, but the date value is optional. Any tips would be helpful. James W. Howe mailto:jwh@allencreek.com Allen Creek Software, Inc. pgpkey: http://ic.net/~jwh/pgpkey.html Ann Arbor, MI 48103