Calculate Total Elapsed Seconds in Microsoft Excel 2010

A little while back a colleague of mine asked me, “How do I calculate the total seconds in Excel?” What he had was a column of timestamps in the h:mm:ss format and he wanted to convert that timestamps to simply display the total seconds, which is actually quite easy to do in Excel depending on (1) how the data was entered, and (2) how the data is formatted. And surprisingly for something simple, it can get quite complicated depending on how much the user understands about Excel Date/Time formats and formatting. To make it easier, I created the following tip: