I have changed the MinDate and RangeMinDate to 1/1/1900 and the control is telling me the date is invalid. I am trying to choose 9/30/1979...Not sure why.
I tried replicating the problem you described but was unable to do so. As you can see in this video I was able to select the mentioned date. Please review the project which I have tested(you can find it in attachments) and tell us what differs in your case. Additionally please specify the version of the controls that you are using.
All the best,
Angel Petrov
the Telerik team
If you want to get updates on new releases, tips and tricks and sneak peeks at our product labs directly from the developers working on the RadControls for ASP.NET AJAX, subscribe to their blog feed now.