For a detailed list with the server-side properties and methods of the control, see the Server-Side API of the RadDatePicker class.
The main classes for working with the RadDatePicker control are:
RadDatePicker is the main class for the date picker control. It provides a rich list of properties, methods, and events for customizing the control, which you can see at Telerik.Web.UI.RadDatePicker.
RadDateInput is the class for the input area of RadDatePicker. It handles the formatting and parsing of date and time strings, and has a number of its own properties, methods and events, which you can find at RadDateInput Server-side Programming Overview.
CalendarPopupButton is the class for the popup button that displays the calendar on RadDatePicker. It is exposed by the DatePopupButton property. The following article Telerik.Web.UI.CalendarPopupButton lists the available server API for the CalendarPopupButton control.