Created Unassigned: ajax popup calender extender not displaying the correct date [27604]

I'm using the ajax pop up calender extender but what ever date i select it store 1/1/1990 in datebase and displays

This is the code
<asp:TextBox ID="TextBox4" runat="server"></asp:TextBox>
<cc1:CalendarExtender ID="TextBox4_CalendarExtender" runat="server"
Enabled="True" TargetControlID="TextBox4">
</cc1:CalendarExtender>

and i'm trying to get the date by TextBox4_CalendarExtender.SelectedDate
point me out where i;m wrong