I am not quite sure what you would like to implement. Would you describe what is your goal in more detail?
In case you would like the popup calendar to have the selected date highlighted, this is available out of the box. You can test the behavior with the following code:
Do you want to have your say when we set our development plans?
Do you want to know when a feature you care about is added or when a bug fixed?
Telerik Feedback Portal
and vote to affect the priority of the items