12-hour clock

(Redirected from 12 hour notation)
A typical analog 12-hour clock

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 Latin: ante meridiem, means "before midday" and Latin: post meridiem means "after midday".[1]

Each period has 12 hours and are numbered 1 or 0 to 12 or 11. 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
24:00/0:00 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
24:00/0:00 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]

12-hour Clock Media

References

  1. "Time". The New Encyclopædia Britannica 28. (1986). 660 2a. 
    "Time". Encyclopædia Britannica. Encyclopædia Britannica Online Library Edition. “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.