Transforming Date formatted as String to Date format

Hi, I am having some trouble using the multi-field formula reformat a date from a string to an actual date data type.  I have a few different dates all coming in as strings that are in different formats, and I would like to use the multi-field formula tool to convert them all to date data type.  

Here are the two different string formats.

          GL Date             Open Date

2007/11/30 00:00:00;   1/17/2008;  

When I run these two fields through the multi-field formula (DateTimeParse([_CurrentField_],'%Y/%m/$m')), I get:

         GL Date             Open Date

       2007-11-01                 Null

Thanks very much for your time.