Story of AM and PM: Meaning, History, and Fun Facts About Timekeeping

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Origin of AM and PM in Timekeeping

We use AM and PM for time, but have you ever wondered about their origin? Learn the full story and interesting history.

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When Sun and Moon Dictated Time

Before clocks, people understood time by day and night. The sun's position indicated the time of day, while the moon and stars guided the night. Ancient Egyptians believed day and night were equal.

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How Was the First Clock Created?

Sundials were used to tell time, with the sun's shadow indicating the hour. Mechanical clocks, initially 24-hour, were used in European church towers. As clocks became portable, 12-hour clocks emerged in the 14th century for easier reading and smaller size.

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How Did AM and PM Become Common?

With the rise of 12-hour clocks, AM and PM were used to distinguish day halves. Though not astronomically linked, they simplified timekeeping.

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What is the Full Form of AM and PM?

AM stands for Ante Meridiem (before noon), and PM stands for Post Meridiem (after noon). 6 AM is morning, 6 PM is evening. AM: 12:00 AM to 11:59 AM. PM: 12:00 PM to 11:59 PM.

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What Happened to the 24-Hour Clock?

By the late 19th century, many countries and militaries favored the 24-hour clock to avoid confusion. However, AM and PM remain common in countries like Australia, Canada, and the Philippines. Notably, the US and Canadian militaries use the 24-hour clock as "military time."

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Interesting Facts About Time

9:35 means 9 hours and 35 minutes. You can write it as 0935 in 24-hour format or with AM/PM in 12-hour format as 09:35 am/ 09:35 pm.