If you set DateFormat string to "MM/yyyy" and the entered value contains only "month" and "year" parts (for example "06/2011"), the embedded parsing mechanism of the RadDateInput control will parse the "month" part as a day and apply the current month to form the final date. In order to avoid the built-in parsing the developer must construct the date manually before it is applied to the input.
On the following code library you could find how to do that:
Additionally the purpose of the RadMonthYearPicker control is to choose month and year. However the .NET framework does not have structure which could keep only month and year, so the MonthYearPicker keeps month and year into the DateTime object. Into this object the date part is populated by default from the picker control. The user could not see the date part and could not change it. The end user could choose or change only month and year. The developers could get the selected date into the code behind and extract the month and year part from it and do whatever they want with this parts. Also into the code behind you could get the entire date object kept into the SelectedDate property of the control and save it into the database or operate directly with it.
the Telerik team