CalendarExtender in Ajax Control Toolkit - basic code

Question

I want to use CalendarExtender from Ajax Control Toolkit.

I want to assign the Calendar to textbox, and want the calendar to be triggered by the clickl on the textbox as in the first example on the toolkit website

My code is as follows:

    <asp:TextBox ID="txt1" runat="server" AutoPostBack="True"></asp:TextBox>
    <ajaxToolkit:CalendarExtender ID="cal1" runat="server" TargetControlID="txt1"></ajaxToolkit:CalendarExtender>

but this does not seem to work as no calendar appears when clicking on the textbox. Am I missing something obvious here? Do I need to fire an explicit event on the textbox and handle it?

Also for some reason the is called ajaxToolkit:Calendar not ajaxToolkit:CalendarExtender in the examples