People 'feel stupid' after discovering what AM and PM actually mean

 People have been left feeling pretty silly after only just learning the origin of the terms AM and PM. While some people consider this common knowledge, others have admitted they had no idea what the terms meant.

Do you use AM and PM when telling the time, or are you more of a fan of the 24-hour clock?People have been left feeling dumb after only just learning what something they say almost every day means. Unless you're a fan of the 24-hour clock, you're probably used to referring to times in the morning with the suffix 'AM', along with 'PM' for the afternoon and evening.

But what exactly does it mean? Some people might consider the origins of the terms to be common knowledge, but others admit they have no idea what they mean.

Writing on X, formerly Twitter, one user asked: "I might be called stupid after this, but WTF does 'AM' and 'PM' stand for?" Fortunately, people were swift to provide clarification.

What do AM and PM mean?

As with much in the English language, the origins lie in Latin. AM is short for "ante merīdiem, meaning "before noon/midday".

PM, on the other hand, means "post merīdiem". This means – you've guessed it – "post noon/midday".

Alt Text: A close-up view of an analog clock displaying the time as approximately 10:10, with the hour and minute hands clearly visible against a white background. The numbers 1 through 12 are marked on the clock face, and the minute hand points between the numbers 10 and 12.

Have you ever thought about what AM and PM mean?

Lots of people have admitted they had never even thought about this. One user commented: "I've never in my life thought to ask this question... lmao."

Another chuckled: "Haha, my wife just said, 'almost morning and past morning?'" And a third remarked: "I bet 5,000 people got the answer to that question from this post, when they didn't even have the question in them before this post. That makes it a great post. It made people think and answered the question."

While some people were genuinely amazed by the discovery, others took a more cynical view of the revelation. One person responded sarcastically: "Wow, this gives me a great idea!

"What if there was some way on the internet that you could search for answers without having to ask specific people? I think a site that could do that might do very well!"

What is the origin of AM and PM?

The application of AM and PM as components of the 12-hour clock format can be traced back to ancient times. The 12-hour timekeeping method itself originates from ancient Egypt and Mesopotamia, where sundials and water clocks were employed to separate the day into distinct segments.

The Romans similarly operated on a 12-hour day, splitting daylight into 12 hours and night time into 12 hours, with lengths that fluctuated according to the seasons. The use of AM and PM became increasingly standardised alongside the formalisation of contemporary clock and timekeeping mechanisms.

The broad acceptance of mechanical clocks during the medieval era and the later standardisation of time throughout the Industrial Revolution helped establish these abbreviations in daily use.