In the insert record behavior, you can modify the binding to reformat the date as it is going into the database.
When you bind a column to a form field it will create code similar to:
<?php echo((isset($_POST["date"]))?$_POST["date"]:"") ?>
you can change that to use the date function to reformat the date:
<?php echo((isset($_POST["date"]))?date("Y-m-d", strtotime($_POST["date"]):"") ?>