OnBlur events are usually fired for input elements only. Therefore, RadControls does not provide blur events for non-input control like the RadCalendar. RadDatePicker's DateInput, which is represented by the textbox, has an OnBlur event you can use.
Other than that, you will need to use an element's click or mouseover event. A scenario you can take is set a flag on mouse over and check the flag on click to see if a mouse is over a particular element when clicked or not.
the Telerik team