jQuery UI Datepicker - default day of month on month change

I need a specific behavior of jQuery UI Datepicker:

By clicking on 'Prev/Next Month' current day of month must be automatically set in the previous/next month.

e.g.: default date was set to 8/25/2011, after clicking 'Next month' (or selecting September in dropdown), 9/25/2开发者_高级运维011 must be automatically selected (but not populated to input and datepicker itself must not disappear, so user can change this default day of month).

Thanks for advice.

---

You can make use of the beforeShowDay event.

var defaultDay = 15;
$('#datepicker').datepicker({
    beforeShowDay: function(date) {
        if (date.getDate() == defaultDay)
            return [1, 'ui-state-highlight ui-state-active'];  // can replace with a customised class
        return [1, ''];
    },
    defaultDate: '07/' + defaultDay + '/2011'
});

You can assign a customised class yourself and style it to your heart's content.

Example: http://jsfiddle.net/william/nNmg2/

Note: you may need to take care of double-digit padding, if defaultDay is 1 to 9.