Military time ... the hour and the last two digits representing the minutes. For example, 1:00 AM is written as 0100 hours, while 1:00 PM is written as 1300 hours. Also called the "24-clock ...

But in 1793, the French smashed the old clock in favor of French Revolutionary Time: a 10-hour day, with 100 minutes per hour ... on their faces (allowing for conversion and confusion).