Well I didn't want to have to ask but I've now spent all afternoon on this and can't even see what you suggested in action because I can't seem to get any results searching on dates.  I apparently just don't have the format right but I don't know what else to try anymore.  Can you tell me how to search on dates?  I'm using SQL geodatabase and the field is the auto-created editor tracking field.
This is what I have currently but have tried tons of things.  I get no errors, just no results.  And I verified that there are some entries in the table to find.  I tried YYYY/MM/DD and appending 00:00:00.  Frustrated!
                    <values>
  <value prompt="From Date (MM/DD/YYYY)">created_date >= '[value]'</value>
  <value prompt="To Date (MM/DD/YYYY)" operator="AND">created_date <= '[value]'</value>
                    </values>
Suggestions? thanks!