ASP.Net Example

<asp:textbox id="txtdate" runat="server"></asp:textbox>


<asp:regularexpressionvalidator controltovalidate="txtdate" errormessage="RegularExpressionValidator" 

id="RegularExpressionValidator1" runat="server"

validationexpression=

"(0[1-9]|[1 2][0-9]|3[0 1]|)[-/.](0[1-9]|1[0 1 2])[-/.](19/20)\d\d ">

</asp:regularexpressionvalidator>