BI Publisher, create Parameter from date field formatted like: 10/22/2010 2:31:14 PM and stored as d

Trying to build a parameter in BI Publisher that will filter the results on date.  Can create the parameter but the parameter does not filter the results by the value entered.  Advised in an SR to use TO_CHAR when creating the data model and then create the Data Type as String and the Parameter Type as Date.  BIP will allow string format on creation but will not maintain that state after saving. When returning to the parameter, the Data Type reverts to Date.   Tried many other approaches including multiple formats using TO_CHAR in the data model but these all fail.