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 Latin ante 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.
The 12-hour time convention is common in several English-speaking nations and former British colonies, as well as a few other countries. In English-speaking countries: "12 p.m." usually indicates noon, while "12 a.m." means midnight, but the reverse convention has also been used (see § Confusion at noon and midnight). "Noon" and "midnight" are unambiguous.
| 24-hour clock | 12-hour clock | |
|---|---|---|
| 00:00 | midnight 12:00 p.m. (start of the day) 12:00 a.m. (start of the day) | |
| 01:00 | 1:00 a.m. | |
| 02:00 | 2:00 a.m. | |
| 03:00 | 3:00 a.m. | |
| 04:00 | 4:00 a.m. | |
| 05:00 | 5:00 a.m. | |
| 06:00 | 6:00 a.m. | |
| 07:00 | 7:00 a.m. | |
| 08:00 | 8:00 a.m. | |
| 09:00 | 9:00 a.m. | |
| 10:00 | 10:00 a.m. | |
| 11:00 | 11:00 a.m. | |
| 12:00 | midday noon 12:00 a.m. (start of the day) 12:00 p.m. | |
| 13:00 | 1:00 p.m. | |
| 14:00 | 2:00 p.m. | |
| 15:00 | 3:00 p.m. | |
| 16:00 | 4:00 p.m. | |
| 17:00 | 5:00 p.m. | |
| 18:00 | 6:00 p.m. | |
| 19:00 | 7:00 p.m. | |
| 20:00 | 8:00 p.m. | |
| 21:00 | 9:00 p.m. | |
| 22:00 | 10:00 p.m. | |
| 23:00 | 11:00 p.m. | |
| 24:00 (00:00 of next day) |
midnight 12:00 p.m. (start of the day) 12:00 a.m. (start of the day) (end of the day) | |