Jefferey, thanks for asking the question and Stuart, thanks for answering it. I was scratching my head over this.
There still needs to be a way to alert the user when the date field reverts, losing the edit they have made. The property change listener does not fire if the value reverts, so you can use this fact to alert the user.
or... you can use the Input Verifier given in the docs for JFormattedTextField to return a true or false that you can use to determine if the date format accepted the date or not.