How to validate dates in ASP.NET

The simpliest way is by using range validator control and define date bounds

<asp:textbox id="textbox1" runat="server">
</asp:textbox>
<asp:rangevalidator id="valRange" runat="server" controltovalidate="textbox1" 
maximumvalue="31/12/2010" 
minimumvalue="1/1/2000" type="Date" 
errormessage="*" display="dynamic">
*
</asp:rangevalidator>