A 13-hour clock has been released as a "tongue-in-cheek" protest about the gender pay gap in New Zealand. It's paired with a diary with an extra month in the year, as part of a publicity campaign ...

Military time, also known as the 24-hour clock, is a system the military uses to eliminate confusion between morning and afternoon hours, since the armed forces are in operation around the clock.

The brain has a master clock that is set by exposure to sunlight and darkness. This circadian rhythm is a roughly 24-hour cycle that determines when we become sleepy and when we’re more alert.