<!DOCTYPE html>
<html>
<head>
<script runat="server">
Sub DaySelect(obj As Object, e As DayRenderEventArgs)
If e.Day.IsSelected Then
If e.Day.IsWeekend = "TRUE" Then
Label1.Text = "YES"
Else
Label1.Text = "NO"
End If
End If
End Sub
</script>
</head>
<body>
<form runat="server">
<asp:Calendar id="cal1" runat="server" OnDayRender="DaySelect"/>
The selected date is in a weekend:
<asp:Label id="Label1" runat="server"/>
</form>
</body>
</html>