1. You need to load the jQuery UI i18n files:
<script src="//ajax.googleapis.com/ajax/libs/jqueryui/1.11.4/i18n/jquery-ui-i18n.min.js">
</script>
2. Use $.datepicker.setDefaults function to set defaults for ALL datepickers.
3. In case you want to override setting(s) before setting defaults you can use this:
var options = $.extend(
{}, // empty object
$.datepicker.regional["fr"], // fr regional
{ dateFormat: "d MM, y" /*, ... */ } // your custom options
);
$.datepicker.setDefaults(options);
The order of parameters is important because of the way jQuery.extend works. Two incorrect examples:
/*
* This overwrites the global variable itself instead of creating a
* customized copy of french regional settings
*/
$.extend($.datepicker.regional["fr"], { dateFormat: "d MM, y"});
/*
* The desired dateFormat is overwritten by french regional
* settings' date format
*/
$.extend({ dateFormat: "d MM, y"}, $.datepicker.regional["fr"]);