Pop-up calender with

Hi, DJAppleboy

<asp:TextBox ID="TextBox1" runat="server"></asp:TextBox>
<cc1:CalendarExtender ID="TextBox1_CalendarExtender" runat="server" OnClientHidden="onCalendarHidden"  OnClientShown="onCalendarShown" BehaviorID="calendar1"
    Enabled="True" TargetControlID="TextBox1">
</cc1:CalendarExtender>

function onCalendarShown() {

     var cal = $find("calendar1");
     //Setting the default mode to month
     cal._switchMode("months", true);

     //Iterate every month Item and attach click event to it
     if (cal._monthsBody) {
         for (var i = 0; i < cal._monthsBody.rows.length; i++) {
             var row = cal._monthsBody.rows[i];
             for (var j = 0; j < row.cells.length; j++) {
                 Sys.UI.DomEvent.addHandler(row.cells[j].firstChild, "click", call);
             }
         }
     }
 }

 function onCalendarHidden()
 {
     var cal = $find("calendar1");
     //Iterate every month Item and remove click event from it
       if (cal._monthsBody) {
         for (var i = 0; i < cal._monthsBody.rows.length; i++) {
             var row = cal._monthsBody.rows[i];
             for (var j = 0; j < row.cells.length; j++) {
                 Sys.UI.DomEvent.removeHandler(row.cells[j].firstChild,"click",call);
             }
         }
     }

 }

function call(eventElement)
        {
            var target = eventElement.target;
            switch (target.mode) {
            case "month":
                var cal = $find("calendar1");
                cal._visibleDate = target.date;
                cal.set_selectedDate(target.date);
                cal._switchMonth(target.date);
                cal._blur.post(true);
                cal.raiseDateSelectionChanged();
                break;
            }
        }

Get complete source code HERE
http://cid-cdbfe38dc780f729.skydrive.live.com/self.aspx/.Public/Calendar%20Extender%20Month.zip[^]

Have a look at the Calendar control in the ASP.Net Ajax toolkit[^].
Once you click on the year or month on top, you can actually navigate through either of them.
It even remembers the state, so next time when you open the popup, you can navigate through months (or years) as required.