[Poohsan]

To tell time in 24 hour increments not 12 increments.

“A 24-hour watch is a type of watch with an hour hand that completes a revolution every 24 hours. This type of watch is especially useful for airplane pilots, astronauts, members of the military, or anyone who uses a 24-hour clock.” – from: http://en.wikipedia.org/wiki/GMT_Watch