U.S. News


Why does the U.S. not use military time?

In Ancient Egypt and Rome, the day and night were divided into 12 hours each.
Posted at 5:32 PM, Mar 14, 2023

If you’re guilty of accidentally setting your alarm on your smartphone for 6 p.m. instead of 6 a.m. —  you’re not alone. 

Most Americans prefer the a.m.-p.m. system instead of the 24-hour clock.  

But why? Historians believe Babylonians came up with the concept of the 12-hour clock. It’s believed they were inspired by the 12 lunar patterns and 12 zodiac signs in their annual calendar. 

In Ancient Egypt and Rome, the day and night were divided into 12 hours each. To tell time, Egyptians used sundials during the day and water clocks at night.   

Centuries later, the first faceless mechanical clock made out of iron came out of England in 1283. The 24-hour analog dial was soon invented and spread across Europe.  

But as the years went by, clockmakers found the 12-hour analog simpler and cheaper. And in the 15th and 16th centuries it became the standard in northern Europe.  

Still, the use of a conceptual 24-hour system has been popular in most of the world since the 19th century.  

Airlines and public transit use 24-hour time to avoid confusion between a.m. and p.m. hours.  

Yet over a dozen countries use the 12-hour clock almost exclusively, as the written and spoken system of time. 

Man with blindfold sleeping.

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