Calender in Cgridview filter

here my model field is update_date

 
 'afterAjaxUpdate'=>"function(){jQuery('#date_purchased_search').datepicker({'dateFormat': 'yy-mm-dd'})}",

    'columns'=>array(
..............................
 array(
     'name' => 'update_date', 'type' => 'raw',
     'filter'=>$this->widget('zii.widgets.jui.CJuiDatePicker',
 array('model'=>$model, 'attribute'=>'update_date',
     'htmlOptions' => array('id' => 'date_purchased_search'), 'options' => array('dateFormat' => 'yy-mm-dd')), true)
 ),

......................

) //end columns