How to add a custom class to my JQuery UI Datepicker

beforeShow can be used to manipulate the class before showing the datepicker.

$('input').datepicker({
   beforeShow: function(input, inst) {
       $('#ui-datepicker-div').removeClass(function() {
           return $('input').get(0).id; 
       });
       $('#ui-datepicker-div').addClass(this.id);
   }
});

Demo (using jQuery 1.6.2 but needs jQuery > v1.4 for the .removeClass() which takes a function)

Note This works by removing all the classes (i.e. <input> ids) with a **general $('input') selector which you might want to limit to just pick up the <input> elements that have been modified into date pickers.

Edit Just had an upvote for this and looking at the code, it did not seem to do what I explained it should (maybe I misunderstood the question!). So, here is a version which adds a class equal to the id of the <input> clicked on to the datepicker. Also uses the original .removeClass() so this will work with jQuery > v1.2.

var inputIds = $('input').map(function() {
    return this.id;
}).get().join(' '); // space separated ready for removeClass

$('input').datepicker({
   beforeShow: function(input, inst) {
       $('#ui-datepicker-div').removeClass(inputIds);
       $('#ui-datepicker-div').addClass(this.id);
   }
});​

Jquery UI custom download allows you to add a custom prefix to your theme, say you added a prefix ".datepicker_wrapper" you can add this class to your datepicker this way :

 $('.datepicker').datepicker({
      beforeShow : function(){
           if(!$('.datepicker_wrapper').length){
                $('#ui-datepicker-div').wrap('<span class="datepicker_wrapper"></span>');
           }
      }
 });

You can try this to add css Classes for multiple datepicker.

But remeber jQuery UI - v1.9.1 is not up-to-date last version is from 2012-10-25

HTML:

<input type="text" id="datepicker1" name='date1'/>
<input type="text" id="datepicker2" name='date2'/>

Jquery:

$('#datepicker1').datepicker( {
    changeMonth: false,
    changeYear: true,
    showButtonPanel: true,
    dateFormat: 'yy',
    showAnim: '',
    beforeShow: function( input, inst){
      $(inst.dpDiv).addClass('just-yaer');
    },
    onClose: function(dateText, inst) { 
        var year = $("#ui-datepicker-div .ui-datepicker-year :selected").val();
        $(this).datepicker('setDate', new Date(year, 1));
        $(inst.dpDiv).removeClass('just-yaer');
    }
});

$('#datepicker2').datepicker( {
    changeMonth: true,
    changeYear: false,
    showButtonPanel: true,
    dateFormat: 'MM',
    showAnim: '',
    beforeShow: function( input, inst){
      $(inst.dpDiv).addClass('just-month');
    },
    onClose: function(dateText, inst) { 
        var month = $("#ui-datepicker-div .ui-datepicker-month :selected").val();
        $(this).datepicker('setDate', new Date(month, 1));
        $(inst.dpDiv).removeClass('just-month');
    }
});

CSS:

.just-yaer .ui-datepicker-prev,
.just-yaer .ui-datepicker-next,
.just-yaer .ui-datepicker-month,
.just-yaer .ui-datepicker-calendar {
    display: none;
}

.just-month .ui-datepicker-prev,
.just-month .ui-datepicker-next,
.just-month .ui-datepicker-year,
.just-month .ui-datepicker-calendar {
   display: none;
}

Working fiddle:

http://jsfiddle.net/g6mnofu2/27/