24-hour clock converter

How to read 24-hour and military time

The 24-hour clock numbers the hours of the day from 0 to 23 instead of repeating 1 to 12 twice. There is no AM or PM, because each hour has its own number. The first twelve hours, from midnight to just before noon, look the same as on a 12-hour clock: 9:30 AM is 09:30. From noon onward you add twelve, so 1:00 PM is 13:00, 3:45 PM is 15:45 and 11:15 PM is 23:15.

Military time is the same clock written without the colon and said aloud in a fixed way. 0730 is “zero seven thirty”, 1300 is “thirteen hundred” and 2145 is “twenty-one forty-five”. Four digits are always used, so a morning hour has a leading zero: 0600, not 600. The word “hours” is often added in speech (“oh-six-hundred hours”), and in the armed forces a letter after the time names the zone, such as 1530Z for 15:30 UTC.

To convert in your head, subtract 12 from any hour from 13 to 23 to get the PM time, and add 12 to a PM hour to get the 24-hour time. The only exceptions are the two hours around the 12 itself, which are covered below.

Midnight, noon, and the 12 that confuses everyone

On a 12-hour clock the hour that follows 11 is 12, and that is where the confusion starts. Noon is 12:00 PM, the first minute after the middle of the day, while midnight is 12:00 AM, the first minute after the middle of the night. Many people believe that 12 AM is noon because AM means “before”, and they are not alone, which is why contracts, tickets and flight itineraries that say “12 AM” or “12 PM” often have to explain themselves. The 24-hour clock removes the problem. Noon is 12:00 and midnight is 00:00.

There is a second midnight. 24:00 is allowed in some conventions, such as ISO 8601 and railway timetables, to mean the end of a day, while 00:00 means the start of the next. A shop that closes at 24:00 on Friday closes at the same instant that Saturday begins at 00:00. Computers almost always use 00:00, and so does the converter above, but it accepts 2400 as input and tells you the equivalent. For schedules that cross midnight, a service that runs from 22:00 to 02:00 is easier to read in 24-hour form than 10 PM to 2 AM, since there is no AM and PM to track.

Who uses which clock

Most of the world writes time on the 24-hour clock: on train and bus timetables, flight boards, medical records, computer logs and official documents. Most of Europe, Latin America and Asia use 24-hour time in writing, and often in formal speech as well. In everyday conversation, though, many of those same countries say “half past three” or “three in the afternoon” and mean 15:30.

The 12-hour clock dominates everyday speech and writing in the United States, Canada (outside Quebec), Australia, India, the Philippines, and a number of other English-speaking and former British countries. The United Kingdom is mixed: people say “half past six” in speech, but rail timetables and most digital signs use 24-hour time. Even in the 12-hour countries the 24-hour clock is the standard in aviation, the military, medicine, emergency services and computing.

If you work across borders, the safe choice for anything that will be read by others is 24-hour time plus a zone, for example 15:00 UTC or 15:00 IST. It removes the AM and PM guess, and it avoids the “12” problem altogether. To convert that time into the readers’ zones, use our time difference calculator or one of the pair converters.

Writing 24-hour time correctly

Writing conventions differ slightly. International standards write 14:05 with a colon, and the military omits it as 1405. Both are understood. Use two digits for the hour and two for the minutes. Do not add AM or PM to a 24-hour time, because 17:30 PM is redundant and 07:30 PM is contradictory. In a technical context, add the zone: 09:00 UTC, 14:30 EST.

For a date and time together, the ISO 8601 format 2026-11-13T17:30:00Z is unambiguous. The Z means UTC. If you need to turn such a time into a number for a database or API, try the Unix timestamp converter.