AP Photo

Everybody knows that there are 24 hours in a day, 60 minutes in an hour, and 60 seconds in minute.* But in 1793, the French smashed the old clock in favor of French Revolutionary Time: a 10-hour day, with 100 minutes per hour, and 100 seconds per minute. This thoroughly modern system had a few practical benefits, chief among them being a simplified way to do time-related math: if we want to know when a day is 70% complete, decimal time simply says “at the end of the seventh hour,” whereas standard time requires us to say “at 16 hours, 48 minutes.”