As of R1 2017 RadDateTimePicker can display and parse dates from all .NET Framework calendar implementations.
A full list of the supported calendars as well as examples of how to set them up can be found in the respective RadCalendar article.
Figure 1 demonstrates the parsing of DateTime values for the Hijri calendar.
Figure 1: Hijri dates parsing
For more information on how to use the calendar classes when working with date values, please read the following MSDN article.