What came first 12 hour or 24 hour clock?
The first mechanical clock dates from the 14th century.
And with that came the switch from 12 to 24 hours: Mechanical clocks brought about a change in the way in which time was measured.
Before the 14th century, the system of dividing a period of one day and one night into 24 equal hours was only used by astronomers..
Why do we use 24 hour time?
The reason airlines, public transit and the armed forces use 24-hour “military” time is to avoid confusion between a.m. and p.m. hours. You can take the same approach with your cell phone’s clock settings to avoid accidentally setting your morning alarm at an afternoon hour.
Why is it important to use AM and PM?
The usage of a.m. and p.m. helps us to convey clearly which section of the day we are talking about. Before introducing am and pm, children should be introduced to the two important terms – noon (midday) and midnight. … Post meridiem means after midday.
Who uses a 12 hour clock?
9) Eighteen (18) Countries use the 12-hour clock: Australia, Bangladesh, Canada, Colombia, Egypt, El Salvador, Honduras, India, Ireland, Jordan, Malaysia, Mexico, New Zealand, Nicaragua, Pakistan, Philippines, Saudi Arabia and U.S. (although the military uses the 24-hour clock).