What is A.M. and P.M. in Time?

What is the Definition of Time? How did Time get divided into 12-Hour and 24-Hour Formats? What is A.M. & P.M.? What is Military Time?
clocks. what is a.m. and p.m. in time

Time once lost never comes back. We all have heard this phrase and understood the meaning & importance of it. Do you remember what is A.M. and P.M. in time or which means day & which indicates night? Let us revise these fundamentals and go back in time!

1. What is Time?

Although it is nearly impossible to define time, let us try. Scientists have defined time as the progression of events from the past to the present and then, from the present to the future. Time is something we cannot see, touch or taste, but we have found ways to measure it. Now, simply speaking, time can also be defined as a duration in which things, events, etc. take place. Time is the indefinite continued progress of existence. The events of the present, past, and future are included in it as a whole. (See How Many Number of Days in a Month?)

2. What are Natural Trackers of Time?

Long before the clocks were invented, the early civilizations used the positions of heavenly bodies like the sun and the moon to measure time. With that reference, time was divided into two cycles: day and night. During that era, the meaning of A.M. and P.M. was not clearly known.

  • So, the day cycle was tracked by the position of the sun.
  • The cycle of the night was tracked from the position of the moon & stars.

Therefore, they were unintentionally following the 12-hour system and answered the query of what is A.M. and P.M. in time.

3. Who Invented the 12-hour Format?

Diving into history, the Egyptian sundial clock used during daytime and Egyptian water clock used during nighttime were found in the tomb of Pharaoh Amenhotep I built around 1500 BC. It is believed that this 12-hour system was invented in ancient Egypt and Mesopotamia. Historic pieces of evidence show that Egyptians took into consideration all 24 hours and then divided it into 12 hours each for easy management of different chores.

Romans also used a 12-hour clock and divided the day into 12 hours. (See What is Grandfather Clock History?)

4. What is A.M. and P.M. in Time?

The abbreviations A.M. and P.M. are derived from the Latin words ante meridiem and post meridiem respectively. We use A.M. from 12 in the night to 11:59 in the afternoon. And we use P.M. from noon to 11:59 in the night. So, we can remember it like this – P.M. means afternoon to midnight, and A.M. is used from midnight till noon. It applies only in the 12-hour format. Thus, this answers what is A.M.and P.M. in time. (See Why Do We Have Different Time Zones?)

5. What is the Correct Usage of A.M. & P.M.?

  • While writing a formal piece of work, it is better to write in lowercase, like a.m. or p.m., with periods in the end.
  • Also, we should avoid writing noon, morning, or evening when we have already written the time in AM/PM style.
  • However, use noon or midnight, instead of 12 p.m. or 12 a.m. respectively.
  • Another thing to be kept in mind is to not use o’clock with a.m. or p.m.

6. Which Countries Use A.M. & P.M. Clock Format?

Many countries use the 24-hour clock rather than the 12-hour clock. The countries where the 12-hour format is commonly used are Australia, Colombia, India, Malaysia, Philippines, Pakistan, Jordan, El Salvador, Bangladesh, Honduras, Canada, Nicaragua, Saudi Arabia, New Zealand, Egypt, Mexico, and the United States of America.

But even in these countries, the military uses a 24-hour clock. The 24-hour format is known as military time. In this format, the time is indicated by the hours passed since midnight, i.e., from 0 to 23. (Also See How many seconds are in a year?)

Now we know what is A.M. and P.M. in time, their abbreviations, and correct usage. Stay tuned for more such info!

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