Am and pm: We explain what the acronyms a. m. and p. m. mean and their equivalence with the 24-hour system. Also, how 12 noon is indicated.
What do the acronyms a. m. and p. m. mean?
In the twelve-hour time system, the dominant system in the world, the day is divided into two equal segments of 12 hours each, called ante meridiem (from the Latin “before noon”), abbreviated a. m.; and post meridiem (from the Latin for “after noon”), abbreviated p. m.
In this way, the hours of each period are numbered from 0 to 12, and these two abbreviations are used to distinguish them from each other. Thus, 8 a. m. is equivalent to 8 in the morning, while 8 p. m. is equivalent to 8 in the evening. The only exception to the rule is noon, since 12 o’clock is always accompanied by the acronym m. (from the Latin meridias, meaning “midday”). You must read about Seasons of the Year once.
These acronyms are always written with a period and separated by a space, and are often indicated on automatic clocks and alarm clocks. They are not used, however, in the 24-hour time system, also known as the military time system, since in this system the hours are counted from 00:00 to 24:00, without room for ambiguity. In some countries, one system or the other is preferred, although the 12-hour system is much more common.
The following is a table of equivalences between both systems:
This 12-hour system was the traditional time system inherited from classical antiquity, and was the only one in existence until the 19th century, when the Canadian inventor and engineer of Scottish origin, Sandford Fleming (1827-1915) proposed the 24-hour time, as part of the creation of the universal standard time, that is, the system of time zones to determine the time anywhere in the world, using the Greenwich meridian as the date change point. Maybe you should definitely read about Winter once.
Why is m. used alone to indicate 12 noon?
If the logic of the 12-hour time system is to divide the day into two equal blocks, one before noon (a.m.) and one after (p.m.), it is normal for doubt to arise as to which of the two blocks corresponds to noon, that is, 12 noon. And the answer is no, since in this case the acronym m. is used to indicate that it is, precisely, noon. On the other hand, for twelve o’clock at night the acronym 12 a. m. is used, since this time occurs at the beginning of the day, twelve hours before the day is half over.
