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What is the full form of AM & PM?

AM: Ante Meridiem, PM: Post Meridiem

AM full form
PM full form

The full form of AM and PM is Ante Meridiem (AM) and Post Meridiem (PM) respectively. Ante Meridiem (AM) means Before noon and Post Meridiem (PM) means Afternoon Noon. Both AM and PM are Latin words, used in a 12-hour clock system to represent before noon and afternoon. These can also be used as A.M. and P.M.

AM and PM

The world today relies on two primary timekeeping systems. The first is the famous 24-hour clock method on which the military time functions. The second is the 12 hour timekeeping system popular in the United States. The twelve-hour timekeeping system is used by the United States, Australia, Malaysia, New Zealand, Columbia, Philippines, Many areas of Canada, and some other countries too.

The invention of the sundial led to the use of a.m. and p.m. since 1500 B.C. in ancient Egypt. The Egyptians are accredited for dividing the day into 24 parts or ‘hours.’ The sundial uses the positions of the sun in the sky to calculate the time changes.

AM and PM are used to distinguish 12-hour time zones in day and night. They divide the 24 hours of the day into two sections, each consisting of 12 hours. The first 12-hour period runs from midnight to noon and is called AM. The second 12-hour period runs from noon to midnight and is called PM.

For example: If I say that I will come at 6.30 pm, it may be confusing that it is 6.30 am or 6.30 pm. Thus, AM and PM are used in a 12-hour clock system to correct this erroneous payoff. Accordingly, 6 am is early in the morning and 6 pm is late in the afternoon.


The 12-hour clock system was used in Mesopotamia and the ancient Egyptian era. An Egyptian Sundial for daytime use and an Egyptian water clock for nighttime use were found in the tomb of Pharaoh Amenhotep I.

In 1500 BCE these clocks divided the respective time of their use into 12 hours. The Romans also used a 12-hour clock system. Daylight was divided into 12 hours and night was divided into four clocks.

24 hour clock


In many countries the 12-hour clock is the predominant written and spoken system, mainly in countries that were part of the former British Empire, for example, the United Kingdom (UK), the Republic of Ireland, the United States, Canada (except Quebec), Australia, New Zealand, India, Pakistan, Bangladesh, Malaysia, Malta and others follow this convention such as Egypt, Mexico and the Philippines.

In most countries, however, the 24-hour clock standard system is used, especially in writing. Some nations in Europe and Latin America use a combination of the two, preferring a 12-hour system colloquially but using a 24-hour system in writing and in formal contexts.


People who use a 12-hour clock system often use phrases such as… in the morning,… in the afternoon, in the evening… and at night. 12 a.m. And 12 p.m. Often the wrong reason is that they are not technically correct. So, it is advisable to use 12 noon instead of 12 pm and 12 midnight instead of 12 am.

To avoid wrong payback conditions, airlines and insurance companies use 12:01 am to mark the start of an event that starts with the day and the end of an event at 11:59 pm Marks that end with a day.

Other full forms of AM and PM

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PM full form
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