Military time explained: how the 24-hour clock works

How does the 24-hour clock work?

A day has 24 hours, and a 12-hour clock counts them twice, which is why every time needs AM or PM. The 24-hour clock counts them once, from 00 to 23, so no hour repeats and nothing needs a label. 1 AM is 01 and 1 PM is 13.

Military time is the 24-hour clock written in one fixed style: always four digits, the hour first and the minutes second, with no colon. So 07:30 becomes 0730 and 18:45 becomes 1845. Civilian timetables often keep the colon. The hours are identical either way, and so is the clock used by ISO 8601, the international standard for writing dates and times, which means 18:00 reads the same in a timetable, a hospital record and a computer log.

The clock face shows both systems together. Midnight sits at the top as 00 and noon at the bottom as 12. The right-hand half is the morning, 00 to 11, and matches the 12-hour clock. On the left-hand half, the afternoon and evening, every hour is the 12-hour number plus 12. The highlighted hour is 15: it is 3 on a 12-hour clock, plus 12.

How do you convert standard time to military time?

Check whether the time is AM or PM, adjust the hour, then write four digits. AM hours keep their number, and PM hours add 12. Step through the example below, which converts 3:45 PM.

Most mistakes come from the same few places. Watch for these when you convert a time by hand:

• Adding 12 to 12 PM. Noon is already 12, so 12:30 PM is 1230, not 2430.
• Forgetting the leading zero. 7:30 AM is 0730. Writing 730 leaves it unclear whether the hour is 7 or 73.
• Leaving the hour at 12 after midnight. 12:15 AM is 0015, because the hour restarts at 00.
• Keeping AM or PM. Once a time is written as 1530, the PM is built in.

How do you convert military time to standard time?

Read the first two digits as the hour. If the hour is 00, the time is 12 AM. If it is 01 to 11, it is AM, with the same hour. If it is 12, the time is 12 PM. If it is 13 to 23, subtract 12 and add PM. For 1845 the hour is 18, and 18 − 12 = 6, so the time is 6:45 PM.

Try it both ways below. The converter runs in your browser and nothing you type is sent anywhere.

How do you say military time out loud?

Military time is spoken in two-digit pairs. Hours below 10 keep their zero, said “zero”: 0800 is “zero eight hundred”. An exact hour takes the word “hundred”, so 1300 is “thirteen hundred” and 2000 is “twenty hundred”. With minutes, say the hour and then the minutes: 1530 is “fifteen thirty” and 2145 is “twenty-one forty-five”. Minutes below 10 keep their zero too, so 0905 is “zero nine zero five”.

Many speakers add “hours” at the end, as in “fifteen thirty hours”. It is optional in most settings, and it is common on the radio.

Is midnight 0000 or 2400?

Both are used, for different moments. A day starts at 0000 and its last minute is 2359. Some bookings, shift patterns and legal deadlines write the end of a day as 2400. That is the same moment as 0000 on the next date, but it carries the earlier date, which is exactly how scheduling mistakes happen.

ISO 8601 numbers the hours 00 to 23 and allows 24:00 only to mean the end of a day. Many organisations avoid 2400 altogether. If a date matters, write 0000 with the new date, or 2359 with the old one.

Why is military time used at all?

On a 12-hour clock, 7:00 can mean morning or evening, and a missed AM or PM can send a person, a flight or a delivery to the wrong time. The 24-hour clock removes the doubt, because 0700 and 1900 can never be confused. For that reason it is standard in armed forces, aviation, emergency services, hospitals and shipping, and it is common in public transport timetables. Military.com sets out the same rules this guide follows: four digits, no colon, and midnight written as 0000.

Everyday speech in the United States and a few other countries stays on the 12-hour clock, which is why the conversion keeps coming up. A nurse reading a shift rota, a traveller reading a boarding pass and a student reading a timetable all meet 24-hour times sooner or later, and the rules on this page cover all of them.

Checklist: reading and writing military time