Teaching Students About AM and PM

What is the meaning of AM?

Once you have established the AM and PM meaning’ with your students, lessons about the 12-hour clock will become much more straightforward.

We think of AM as the morning; any time with am after it, your students should regard it as the morning time. The term AM is an abbreviation of the Latin phrase ‘Ante Meridiem,’ which translates to ‘before midday.’

What is the meaning of PM?

You can think of PM as the opposite of AM. Therefore, we associate PM with the afternoon and evening. The term pm is an abbreviation of the Latin ‘Post Meridiem’, which translates to ‘after midday.’ These time indications are centered around Midday, as this is how the 12-hour clock functions. When using a 24-hour clock, the am and pm indications are unnecessary as the hours 1-12 are not repeated.

Do you need to capitalize AM and PM?

When used in a sentence, it is standard not to capitalize the am and pm. Also, it isn’t required that am and pm are used when the phrase already indicates the time, so we wouldn’t say ‘this afternoon pm,’ as the time is already indicated by the word ‘afternoon.’

Time can be very confusing for people as it’s a broad concept to try to understand. For example, it cannot be clear that 12 pm is the middle of the day when we associate it with nighttime. An excellent way to remember this is that 12 am means the start of the day, and even though that feels like the middle of the night to most people, the date changes at 12 am, and the start of a new day begins.

When are AM and PM not used?

As well as the 12-hour clock, there is also the 24-hour clock. The 24-hour clock is also known as the military clock. The 24-hour clock begins at 00:00 at the start of a new day, which means 12 am in 12-hour clock speak. However, a day reaches 23:59, and the clock resets to 00:00; the 24-hour clock is sometimes easier as the numbers aren’t repeated. However, instead of seeing 2 pm, your students will have to recognize this time as 14:00, as it is the 14th hour of that day at 2 o’clock.

It is better to firmly establish the use of the 12-hour clock before introducing the 24-hour clock to your students.

Why does a day have 24 hours?

Now we know the meaning of am and pm, but why do we signify one day by the time of 24 hours? It is believed to date back to the Ancient Egyptians. The Egyptians used a shadow clock, dividing the day into 10 hours. The Egyptians would also add an hour on either side of these 10 hours as ‘twilight hours.’ Night and day were unequal in Egyptian times and changed with the seasons. So in Summer, the days were long, and the nights became shorter- the opposite happened in Winter.

Here are some cool facts about Time that will get your class thinking:

  • When the Dinosaurs roamed the earth, there were 370 days in a year (we now have 365 days in a year). This is because the Earth’s spin is gradually getting slower, which means we are progressively losing days.
  • On Mercury, a single day is two years long concerning time here on Earth.
  • The Great Western Railway is why we use standard London time in the UK today. In the 19th century, each area of the UK had its concept of time. So, for example, Midday in Bristol was a different time from Midday in Sheffield. This was figured out because people kept missing their connecting trains. So to put a stop, London time was used throughout the UK with the introduction of the Great Western Railway.
  • A day is 23 hours, 56 minutes, and 4.2 seconds longer than 24 hours. This is how long it truly takes for the Earth to rotate.
  • There are 31,566,926 seconds in a year.
  • In 1930 Joseph Stalin abolished weekends in Soviet Russia to improve productivity. This was introduced in 1931 and finally returned to a 7-day week ten years later!
  • There are 250 babies born a minute across the world. This equates to 5 babies every second.
  • Mcdonald’s sells 375 burgers every 5 seconds.
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