Hi Priyanka,
Assuming that both Date Widgets are on same form and screen.
Include a JS widget with below script that listens to first Date Widget variable(id_selected_date). and make the second Date Widget as Inactive from Rules Tab.
var tmp = RMPApplication.getVariable(id_selected_date);
RMPApplication.setVariable(id_populated_date,tmp);
Let me know, if your requirement is different.
Regards,
Murali