//Java Script For date Check
<script type="text/javascript">
function checkDate(val) {
if (val != "") {
var r = false;
if (!val.value.match(/^\d{2}\/\d{2}\/\d{4}$/)) {
alert("Invalid Date");
val.value = "";
}
else {
var arr = val.value.split('/');
var d = new Date(arr[2], arr[1] - 1, arr[0]);
if (d.getMonth() + 1 != arr[1] || d.getFullYear() != arr[2] || d.getDate() != arr[0]) {
alert("Invalid Date");
val.value = "";
}
else
r = true;
}
if (r == false) val.select();
return r;
}
}
</script>
// Your HTML TextBox Code Like Below:
<asp:TextBox runat="server" ID="txtDate" onblur="return checkDate(this);"></asp:TextBox>