Times of Day: 12 h (a.m., p.m.) and 24 h Formats - Calculator

Convert and correct representations of 12-hours and 24-hours clocks. While most countries prefer the 24-hour clock, in English-speaking countries and in Latin America the 12-hour clock is common, where twice a day it is 12 o'clock, at midnight and at noon. To distinguish between both, a.m. (ante meridiem, Latin for before midday) respectively p.m. (post meridiem, Latin for past midday) is added.
• in the 12-hour format, a day begins midnight at 12:00 a.m., one hour later it is 1:00 a.m. in the morning, noon is at 12:00 p.m., next is 1:00 p.m. in the afternoon. The last minute of the day is at 11:59 p.m. in the evening. There is no 0:00 o'clock.
• in the 24-hour format, the day begins at 0:00 o'clock, noon is at 12:00 o'clock and the day ends at 23:59 o'clock. There is no 24:00 o'clock.

12-hours clock: a.m.p.m.

24-hours clock: o'clock

Here one format can be converted into the other. Please enter the hours into one clock. The minutes are the same for both clocks and so don't need to be entered. Incorrect input, like 13 a.m. or 25 o'clock, will be corrected.

Last updated on 02/28/2026. Author: Jürgen Kummer

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