Topic summary
Post meridiem
Extracted from the Wikipedia article 12-hour clock.
The 12-hour clock is a time convention in which the 24 hours of the day are divided into two periods: a.m. (from Latinante meridiem, translating to "before midday") and p.m. (from Latin post meridiem, translating to "after midday"). Each period consists of 12 hours numbered: 12 (acting as 0), 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, and 11. The 12-hour clock has been developed since the second millennium BC and reached its modern form in the 16th century.