The client-side DayRender
event is fired for every calendar
day cell when the calendar is rendered as a result of client-side
navigation. This event can be used to apply final changes
to the output (content and visual styles) just before the content is displayed.
Checkout the following demo which shows how to utilize the DayRender client event to customize the
appearance of the rendered date.
Also checkout the forum link: Disable DatePicker Calendar Date on Client Side DayRender
I hope this will help you in getting started.