学步园

方法1：

$( "#datepicker" ).datepicker({
      showButtonPanel: true,
      beforeShow: function( input ) {
        setTimeout(function() {
          var buttonPane = $( input )
            .datepicker( "widget" )
            .find( ".ui-datepicker-buttonpane" );
          
          $( "<button>", {
            text: "Clear",
            click: function() {
              $.datepicker._clearDate( input );
            }
          }).appendTo( buttonPane );
        }, 1 );
      }
    });

方法2：

$(".datepicker").datepicker({
    showButtonPanel: true, 
    closeText: 'Clear',
});

$.datepicker._generateHTML_Old = $.datepicker._generateHTML; 
$.datepicker._generateHTML = function(inst) {
    res = this._generateHTML_Old(inst); 
    res = res.replace("_hideDatepicker()","_clearDate('#"+inst.id+"')"); 
    return res;
} 

参考资料：

http://bugs.jqueryui.com/ticket/3999

http://jsbin.com/ofare/1/edit