What Do AM & PM Mean?


Ever wondered what “AM” & “PM” actually mean, or where these terms come from?

This is important to know, in order to fully understand our 12 Hour Clock System.

A.M. comes from the Latin, “Ante Meridiem“, which means “Before Midday”.
[Latin ante, before + merīdiem, accusative of merīdiēs, midday.]

P.M. comes from the Latin, “Post Meridiem“, which means “After Midday”.
[Latin post merīdiem : post, after + merīdiem, accusative of merīdiēs, midday.]

The 12 Hour Clock System was originally developed in Mesopotamia, Ancient Egypt and Ancient India in the mid-second millennium B.C and has its origins in sundials, which were actually the first clocks. This explains why the ‘meridian’ or halfway point was chosen to be noon instead of at midnight (just go ahead and try using a sundial at night – it’s like eating soup with a fork!).

In Ancient Egypt, water clocks were later developed for use in the P.M., when the sun is no longer available as a means of measuring the passage of time.

The terms “AM” and “PM” first came into widespread use in the English language in the 17th century.

Countries where the 12 Hour Clock System is currently used as the main system of time include:

  • United States
  • Australia
  • Malaysia
  • New Zealand
  • Columbia
  • Philippines
  • New Zealand
  • Canada (with the exception of French communities like Quebec).

But most of the world actually uses the 24 Hour Clock System (referred to as “Military Time” in the U.S.A.), and OnlineClock has already argued, in a separate post, that the 24 Hour Clock System is superior to the 12 Hour Clock System.

So now you know the origins of “AM” and “PM“.

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