The default minimum date for the RadDatePicker is 01/01/1980. So, when you try to assign the value this than this date you will get the below error:
if you will set the Mindate of RadDatePicker to a minimum range than this will fix the issue
ID="RadDateofBirth" DateInput-DateFormat="dd/MM/yyyy" MinDate="01/01/1940" DateInput-DisplayDateFormat="dd/MM/yyyy" runat="server">
This will solved the issue.
if you will set the Mindate of RadDatePicker to a minimum range than this will fix the issue
This will solved the issue.