We will learn about the use of antemeridian and postmeridian.
In English system the day starts at midnight and ends at the next midnight.
The day begins just after 12 o’clock at midnight. The next 12
o’clock in the day time is called midday. Then the next 12 o’clock is
the next midnight.
The time from a midnight to coming midday is called antemeridian. It is written in short as a.m. We say the time between midnight and noon is called a.m.
The time between 12 o’clock of the day, i.e., midday to next midnight is known as postmeridian. It is written in short as p.m.
We say the time between midday (noon) to next midnight is called p.m.
Antemeridian (a.m.) and Postmeridian (p.m.) are Latin words which mean midnight to noon (a.m.) and noon to midnight (p.m.). We use a.m. to express the time between 12:00 midnight and 12:00 noon. We use p.m. to express the time between 12:00 noon and 12:00 midnight.
Our general clock expresses the time of both time periods by the same numbers. We affix a.m. for the time between midnight and noon and p.m. for the time between noon and midnight.
It can either be 8 o’clock before noon or after noon, because the two
hands (hour hand and minute hand) are in the same position on the dial
of the clock. We affix a.m. for the time before noon and p.m. for the
time after noon, so, we write 8 a.m. or 8 p.m.
We often go to school at 7 a.m. and return home at 2 p.m. Offices
often open at 10 a.m. and close at 5 p.m. We go to be bed at 10 p.m. in
the night and get up at 6 a.m. in the morning.
The time before 12:00 noon is expressed as a.m. and the time after 12:00 noon is expressed as p.m. When it is 12 0'clock at night, we say it is 12:00 midnight or 00:00 hour. When it is 12 o'clock during day, we say it is 12:00 noon or 12:00 hours.