I came across a situation where the customer would like to be able to submit a form with an empty date field.  Even though I left the field as not required, the form forces the user to provide a valid input. In this particular situation this effectively makes the date field required, so I found a workaround for them. 

This behavior is not consistent with the un-required single line text field's behavior.  For consistency purposes it would make sense to allow for a null value on date fields.