Can you please add a property CustomFormat to RadDateTimePicker? Possibly we should have 3 options for DisplayMode: Short, Long and Custom. If Custom is selected, user can specify format into CustomFormat field. Ex. CustomFormat = "MMM dd, yyyy". Also, make this field bindable, so that it can be specified from the ViewModel.
When set DateSelectionMode="Month" and SelectionMode="CenturyView", the calendar in the dropdown starts from YearView instead of CenturyView