The End property is usually specified by the Start and Duration properties, and is always calculated as End = Start + Duration. When setting the End property, the Start property retains its value, and the Duration is changed according to the new value of the End property. If the new End property's value is less than the Start property's value, then an exception will be raised.
At setting this property, if it's time is not equal 0:00, or value is equal to the value of Start property, the AllDayEvent property will be set to false.