Hi Gouse,

You could try below BR.

(function executeRule(current, previous /*null when async*/) {
	
	var parentChange = current.change_request.getRefRecord();
	
	if (parentChange.isValidRecord()) {
		current.planned_start_date = parentChange.start_date;
		current.planned_end_date = parentChange.end_date;
	}


})(current, previous);

Please mark correct/helpful if applicable.

Regards,

Shubham