From Stephen Peters:
How long is a lunch hour on Mars?An hour you might think? Well, actually...It turns out that average length of a day on Marsa "sol"is approximately 24 hours and 40 minutes. Since this is so close to Earth's 24-hour day, scientists and engineers operating spacecraft on the surface of Mars have found it convenient to think of a sol as consisting of 24 slightly longer "Mars hours", divided into correspondingly longer "Mars minutes" and "Mars seconds".Use this simple app to convert both ways between Earth durations and Mars durations.Pick a duration.Select Earth-to-Mars or Mars-to-Earth conversion.Tap displayed durations to toggle between hh:mm:ss and total seconds.Oh! And that lunch hour on Mars? It's 1 hour, 1 minute, and 39 seconds.