The RadDatePicker control supports keyboard navigation using the tab or arrow keys:
Tab key Navigation - Once focus is on the RadDatePicker control, the TAB key and SHIFT+TAB key combination move through the parts of the control. The first time the user presses the TAB key, focus moves to the date input area, where the user can type a date value. Pressing the TAB key second time moves focus to the date popup button. Pressing the ENTER key when focus is on the date popup button causes the calendar popup to show. Once the calendar popup is showing, it enters the tab sequence, and behaves like the RadCalendar control.
Arrow key Navigation - Users can navigate within the input area of a RadDatePicker control using the arrow keys:
The left and right arrow keys move the cursor one position to the left or right. When the shift key is pressed at the same time, the left and right arrow keys extend or contract the current selection on position to the left or right.
The up and down arrow keys increase or decrease the value of the date part or time part that contains the cursor when the DateInput.IncrementSettings.InterceptArrowKeys property is true. The DateInput.IncrementSettings.Step property specifies the number of months, days, years, hours, minutes or seconds by which the value changes.