The wizard will automatically convert the date format for you whenever your field datatype is set to be a date.
If you use the server behaviors manually, then you can convert the date format using php... so to display the date from a database use:
<?php echo(date('m-d-Y',strtotime($row_recordset['datecolumn']))); ?>
and to insert from a form field use:
<?php echo(date('Y-m-d',strtotime($_POST['FormField']))); ?>
That way you can display whatever format you want to use and it will store and retrieve the correct format from the database.