All Telerik .NET tools and Kendo UI JavaScript components in one package. Now enhanced with:
function changeEndDate(startDateID, Duration, endDateID) {
var startDateObj = $find(startDateID);
var durat = $find(Duration).get_value();
var endDateObj = $find(endDateID);
var newMinDate = startDateObj.get_selectedDate();
var findur = durat - 1;
var date = new Date();
date.setDate(newMinDate.getDate() + findur);
endDateObj.set_selectedDate(date);
}