Jam 12 jam
Jam 12 jam merupakan kelaziman waktu yang mana 24 jam dalam sehari terpecah kepada dua kala: a.m. (dari bahasa Latin ante meridiem, bererti "sebelum tengah hari") dan p.m. (post meridiem, "selepas tengah hari"). Setiap kala terdiri daripada 12 jam yang berbilang: 12 (yang berfungsi sebagai sifar), 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, dan 11.
Jam 12 jam dimajukan sepanjang zaman dari pertengahan alaf kedua SM ke abad ke-16 M.
| Sistem 24 Jam | Sistem 12 Jam |
|---|---|
| 00:00:00 - 00:59:59 | 12:00:00 tengah malam - 12:59:59 tengah malam |
| 01:00:00 - 01:59:59 | 01:00:00 pagi - 01:59:59 pagi |
| 02:00:00 - 02:59:59 | 02:00:00 pagi - 02:59:59 pagi |
| 03:00:00 - 03:59:59 | 03:00:00 pagi - 03:59:59 pagi |
| 04:00:00 - 04:59:59 | 04:00:00 pagi - 04:59:59 pagi |
| 05:00:00 - 05:59:59 | 05:00:00 pagi - 05:59:59 pagi |
| 06:00:00 - 06:59:59 | 06:00:00 pagi - 06:59:59 pagi |
| 07:00:00 - 07:59:59 | 07:00:00 pagi - 07:59:59 pagi |
| 08:00:00 - 08:59:59 | 08:00:00 pagi - 08:59:59 pagi |
| 09:00:00 - 09:59:59 | 09:00:00 pagi - 09:59:59 pagi |
| 10:00:00 - 10:59:59 | 10:00:00 pagi - 10:59:59 pagi |
| 11:00:00 - 11:59:59 | 11:00:00 pagi - 11:59:59 pagi |
| 12:00:00 - 12:59:59 | 12:00:00 tengah hari - 12:59:59 tengah hari |
| 13:00:00 - 13:59:59 | 01:00:00 petang - 01:59:59 petang |
| 14:00:00 - 14:59:59 | 02:00:00 petang - 02:59:59 petang |
| 15:00:00 - 15:59:59 | 03:00:00 petang - 03:59:59 petang |
| 16:00:00 - 16:59:59 | 04:00:00 petang - 04:59:59 petang |
| 17:00:00 - 17:59:59 | 05:00:00 petang - 05:59:59 petang |
| 18:00:00 - 18:59:59 | 06:00:00 petang - 06:59:59 petang |
| 19:00:00 - 19:59:59 | 07:00:00 malam - 07:59:59 malam |
| 20:00:00 - 20:59:59 | 08:00:00 malam - 08:59:59 malam |
| 21:00:00 - 21:59:59 | 09:00:00 malam - 09:59:59 malam |
| 22:00:00 - 22:59:59 | 10:00:00 malam - 10:59:59 malam |
| 23:00:00 - 23:59:59 | 11:00:00 malam - 11:59:59 malam |
| * Rujuk "Perbezaan penyataan tengah hari dan tengah malam" | |