12-hour clock

time counting system, divided into two parts: AM and PM
(Redirected from Ante meridiem)

The 12-hour clock is a way of dividing the 24 hours of the day into two sections. The two halves are called ante meridiem (a.m.) and post meridiem (p.m.). Both names are from Latin and ante meridiem, means "before midday" and post meridiem means "after midday".[1]

A typical analog 12-hour clock

Each period has 12 hours and are numbered 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11 and 12. Time from midnight to noon is a.m. and from noon to midnight p.m. The table at right shows how it relates to the 24-hour clock.

24-hour clock 12-hour clock
00:00 12:00 AM, midnight

(start of day)

01:00 1:00 AM
02:00 2:00 AM
03:00 3:00 AM
04:00 4:00 AM
05:00 5:00 AM
06:00 6:00 AM
07:00 7:00 AM
08:00 8:00 AM
09:00 9:00 AM
10:00 10:00 AM
11:00 11:00 AM
12:00 12:00 PM (noon)
13:00 1:00 PM
14:00 2:00 PM
15:00 3:00 PM
16:00 4:00 PM
17:00 5:00 PM
18:00 6:00 PM
19:00 7:00 PM
20:00 8:00 PM
21:00 9:00 PM
22:00 10:00 PM
23:00 11:00 PM
24:00 12:00 AM, midnight

(end of day)

World map showing the usage of 12 or 24-hour clock in different countries
  24-hour
  24-hour (12-hour orally)
  Both in common use
  12-hour

The 12-hour time is common in several English-speaking countries and former British colonies (such as the United Kingdom, the United States, the English speaking parts of Canada or India), as well as a few other countries. There is no widely accepted convention for how midday and midnight should be represented: in English-speaking countries, "12 p.m." means 12 o'clock noon, while "12 a.m." means 12 o'clock midnight.[2][3][4]





References

change
  1. "Time". The New Encyclopædia Britannica. Vol. 28. 1986. pp. 660 2a.
    "Time". Encyclopædia Britannica. Encyclopædia Britannica Online Library Edition. Retrieved 20 November 2013. The use of AM or PM to designate either noon or midnight can cause ambiguity.
  2. "Is noon 12 am or 12 pm?". Royal Museums Greenwich. Retrieved 2023-01-26.
  3. "U.S. Government Printing Office Style Manual - Chapter 12 - Numerals". govinfo.gov. Retrieved 2023-01-27.
  4. "time of day, elapsed time". Resources of the Language Portal of Canada. 2020-10-22. Retrieved 2023-01-27.