//replace(/\-/g, "\/")是根据验证表达式把日期转化成长日期格式

 var sDate = new Date(document.getElementById_x("datetimepickerStart").value.replace(/\-/g, "\/"));
    var eDate = new Date(document.getElementById_x("datetimepickerEnd").value.replace(/\-/g, "\/"));

    if(sDate > eDate)
    {
     alert("结束日期不得小于开始日期！");
     return false;
    }
    return true;
}