12-hour clock

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

The 12-hour time convention is common in several English-speaking nations and former British colonies, 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." indicates 12 o'clock noon, while "12 a.m." means 12 o'clock midnight.[4][5][6]

Table info: 12-hour, 24-hour...
Clock system
Midnight (start of day)
12 midnight
12:00 a.m.[lower-alpha 1]
12:01 a.m.00:01
1:00 a.m.01:00
11:00 a.m.11:00
11:59 a.m.11:59
12 noon
12:00 p.m.[lower-alpha 1]
12:01 p.m.12:01
1:00 p.m.13:00
11:00 p.m.23:00
11:59 p.m.23:59
Midnight (end of day)
or shown as start of next day
[lower-alpha 1]