What is the full form of AM and PM?
AM and PM originated from the Latin language, are being used to denote Before Noon and After Noon both respectively. You can see them as A.M. & P.M. in many watches.
AM Full form:AntiMeridiem
PM Full form: Post Meridiem
AM stands for Anti Meridian, meaning before midday whereas PM stands for Post Meridiem, meaning after midday in English. Thus dividing any day into 2 parts: before noon and afternoon. This makes two time zones of 12 hours each. AM starts from 12 am to 12 pm, i.e., from midnight till noon. Then from 12 pm to 12 am, i.e., from noon till midnight is classified as PM. So, we have numbers 1 to 12 and a suffix AM/PM so that every hour of the day can be uniquely identified.
Let’s take an example:
If someone says that they will meet us at 8 O’clock, there will be 2 possibilities: One is in the morning at 8, and another in the evening. AM and PM are helpful in distinguishing these two in 12-hour clock system. Thus, 8 AM means 8 O’clock in the morning and 8 PM means in the evening.
AM: The time from midnight of the day till noon, i.e., from 12:00 AM till 11:59 AM. Example: School at 9 AM means school at 9 O’clock in the morning.
PM: The time from noon to the time when midnight is just about to start, i.e., from 12 PM till 11:59 PM. Example: One goes to be at 10 PM means 10 O’clock in the late evening.
Important: One often gets confused in 12 AM and 12 PM, technically they are wrong. To avoid the confusion, it is spoken as 12 noon as a replacement for 12 PM and 12 midnight as a replacement for 12 AM. All the airlines and insurance organizations take 12:01 as the start the day and 11:59 signifies the end of the day.
The phenomenon of day and night of any date in a calendar is the main reason why any day can be divided into two rounds. In the beginning, a day was considered of two cycles, one of them was denoted by the location of the Sun during daytime and the second one by the position of moon or stars during night time. So, this process divided the whole day into two 12 hours cycles which commenced from midnight and noon.
This system is as old as Ancient Egypt and Mesopotamia. Originated from Egypt sundial and water clock, they are used for daytime and night-time. This can be traced back to 1500BC as both of them were found in the tomb of Pharaoh Amenhotep I and were used in the 12-hour system.
The Romans took the help of daylight and equally divided the time into 12 partitions. This resulted in variation of the daytime during a year because of change in seasons. Also, the night time was divided into 4-time frames for ease.
In the 14th century, mechanical clock was invented which consisted of dials for the 24 hours in a day. This is because of the comparison with Astrolabe and sundial. Whereas in the North of Europe, the clocks generally had a 12-hour system in Roman Numerals, showing Am and PM alternatively. In Italy, the clocks had 24-hour numberings in roman letters. And the British Empire had the 12-hour system.
In the 15th and 16th centuries, the northern system adopted the 12-hour system completely for all of the purposes. The astronomical clocks & chronometers still used the 24-hour dial system.
We can see the 12-hour system is used vastly and widely these days. The shorter hand depicts the hours and it is completely rotated in 12 hours with the help of mechanism. For the countries where they use the 24-hour clock system, another ring numbered from 13 to 24 is attached and synced with the 1-12 hour ring. Thus helping them to read the time easily after 12 of noon.
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