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 , means "before midday" and means "after midday".
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.
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, "12p.m." means 12 o'clock noon, while "12a.m." means 12 o'clock midnight.
References
Time
Clocks