Hi did you see my post earlier? showthread.php?t=30300
you need to make sure your storing the date in reverse order in the database. For example: 2013-03-03 20:02:39, so in the date picker server behaviour under "Format" chose yyyy-mm-dd from the drop down list since it needs to match the format stored in the MySQL database.
My webassist forum link above gives a more in depth guide to date usage.