Terry,
Adding 1 to a timestamp attribute will increase its value by one hour. So you are right, you need to add 24 to a timestamp attribute to increase its value by a day.
It is also possible to add a value of type Duration to a Timestamp. We will be implementing a function shortly to specify an arbitrary duration value including seconds, minutes, hours, etc. This function will make it possible to change a timestamp value by any desired time interval.