post meridiem

time period

Also known as: PM, p.m.

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Last updated

July 17, 2026

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"Post meridiem" is a Latin phrase meaning "after midday." It is used in the 12-hour clock system to denote the period from noon to midnight. The abbreviation for post meridiem is PM, P.M., or pm. This system divides the 24-hour day into two 12-hour periods, with AM representing "before midday" and PM representing "after midday". The use of a 12-hour division has historical roots in ancient civilizations like the Babylonians and Egyptians, who used celestial bodies and lunar patterns to structure their timekeeping.123

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12-hour clock
…referred to using pm, meaning post meridiem, or “after midday.” This nomenclature is based on the position of the Sun in relation to the meridian. In writing, periods can be added or omitted and lowercase letters can be replaced by their uppercase counterparts, resulting in “a.m.,” “am,” or “AM” and…
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…referred to using pm, meaning post meridiem, or “after midday.” This nomenclature is based on the position of the Sun in relation to the meridian. In writing, periods can be added or omitted and lowercase letters can be replaced by their uppercase counterparts, resulting in “a.m.,” “am,” or “AM” and…
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What Do am and pm Stand For?
…in Latin, while pm means post meridiem, or “after midday.”
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…in Latin, while pm means post meridiem, or “after midday.”
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