For pre-filling the date question type via URL parameters, the value needs to be entered in the proper date format. While you can add text as the value, it will not be pre-filled in the response area as it only supports proper dates. The allowed date formats are shown below.
mm-dd-yy
mm-dd-yyyy
mm/dd/yy
mm/dd/yyyy
yyyy/mm/dd
yyyy-mm-dd
The field code can be used in URL parameters, as shown below.
https://example.neetocal.com/meeting-with-oliver-smith?dob=10/23/2005