jquery时间日期三级联动

  <%@ Page Language="C#" AutoEventWireup="true" CodeFile="Default3.aspx.cs" Inherits="Default3" %>

  <!DOCTYPE html>

  <html xmlns="http://www.w3.org/1999/xhtml">
  <head runat="server">
  <meta http-equiv="Content-Type" content="text/html; charset=utf-8"/>
      <script src="js/jquery-1.7.2.min.js"></script>
      <title></title>
 </head>
 <body>
     <form id="form1" runat="server">
     <div>
         <asp:DropDownList ID="dr_year" runat="server"></asp:DropDownList>年
         <asp:DropDownList ID="dr_month" runat="server"></asp:DropDownList>月
         <asp:DropDownList ID="dr_day" runat="server"></asp:DropDownList>日
     </div>
     </form>
 </body>
 </html>
 <script>
     var days = ;
     years();
     months();
     Days();
     var date = new Date();
     $("#dr_year").val(date.getFullYear());
     $("#dr_month").val((date.getMonth() + ));
     $("#dr_day").val(date.getDate());
     $("#dr_year").change(function () {
         months();
         Days();
     });

     $("#dr_month").change(function () {
         Days();
     });
     function years()
     {
         for(var i=;i<=;i++)
         {
             var str = "<option value=\"" + i + "\">" + i+ "</option>";
             $("#dr_year").append(str);
         }
     }
     function months() {
         $("#dr_month").empty();
         for (var i = ; i <= ; i++) {
             var str = "<option value=\"" + i + "\">" + i + "</option>";
             $("#dr_month").append(str);
         }
     }
     function Days() {
         $("#dr_day").empty();
         if (parseInt($("#dr_month").val()) ==  || parseInt($("#dr_month").val()) ==  || parseInt($("#dr_month").val()) ==  || parseInt($("#dr_month").val()) ==  || parseInt($("#dr_month").val()) ==  || parseInt($("#dr_month").val()) ==  || parseInt($("#dr_month").val()) == ) {
             days = ;
         }
         else if (parseInt($("#dr_month").val()) ==  || parseInt($("#dr_month").val()) ==  || parseInt($("#dr_month").val()) ==  || parseInt($("#dr_month").val()) == ) {
             days = ;
         }
         else {
             if (parseInt($("#dr_year").val()) %  ==  || (parseInt($("#dr_year").val()) %  ==  && parseInt($("#dr_year").val()) %  != )) {
                 days = ;
             }
             else {
                 days = ;
             }
         }
         for (var i = ; i <= days; i++) {
             var str = "<option value=\"" + i + "\">" + i + "</option>";
             $("#dr_day").append(str);
         }
     }
 </script>