# I Built a Duration Calculator

I get very frustrated when I have to add up durations of time to figure out a total amount of time. The basic communication class at Purdue (COM 114, a presentational speaking class) is being revamped this year. As part of that revamping, the class has gained an “Asynchronous Presentation.” I am a big supporter of this presentation, which amounts to a recorded narration over a PowerPoint-style visual aid, because it uses a lot of important skills for types of presentations that are not taught as well as they could be. I needed to add up the amount of time that students used on each slide to get a total duration for the presentation (some students didn’t set their presentations to automatically advance, so timing the entire presentation was inconsistent).

I have had several times over the last few years where I have needed to add durations of time together, and I have never found a quick and easy way to do it. Excel is typically my go-to application for quick calculations, but it will not handle duration. For no discernible reason, all times in Excel are treated as times of day and not durations. This comes with a number of additional problems, not the least of which is that Excel always stores all of these times of day as a decimal value representing the proportion of the day which has passed (so 12:00 noon is stored as 0.5, and 9:00 in the morning is stored as 0.375, since by 9:00 am 3/8ths of a day has already elapsed. Because of this, if I enter that a student’s introduction lasted 3 minutes and 2 seconds, Excel stores that number as 12:03:02. This has huge implications when you start adding amounts of time together, because Excel keeps trying to add times of day and not amounts of time.

Long story short, I couldn’t find anything online and I got tired of doing it by hand, so I wrote a quick application which can do it. I wrote one version that includes hours, minutes, and seconds and a second version that only includes minutes and seconds (either version can also handle decimal values in the seconds position, should you require more precision.

Here are links to the HMS Duration Calculator and the MS Duration Calculator.