I'm using some data that came from an IVR system. Many of the numbers I am using are time intervals formatted as HH:MM:SS like speed of answer, length of call, etc. I need to sum these numbers and also get them to sum in a pivot table, but they will not. I have tried every format that remotely looks like it might be relevant to what the value represents, but no luck. Only sums to zero. I am not interested in time of day, only the measurement of length of time using HH:MM:SS. What can I do to these numbers to get them to add up?