jQuery Datepicker localization

I need a french calendar and I can't understand the problem. I guess I'm not using the regional options like it should be. But...

Here is my code :

$(function() {
  $('#Date').datepicker({
      showMonthAfterYear: false,
      showOn: 'both',
      buttonImage: 'media/img/calendar.png',
      buttonImageOnly: true,
      dateFormat:'d MM, y'
    },
    $.datepicker.regional['fr']
  );
});