How the 24-hour clock works
The 24-hour clock, called military time in the US, numbers the hours straight through from 00 to 23 instead of resetting at midday. The first hour of the day is 00, so midnight is 00:00, one in the morning is 01:00, noon is 12:00 and the hours keep climbing through the afternoon: 13:00, 14:00 and so on up to 23:59 just before the next midnight. Military style drops the colon and pads to four digits, so 2:30 pm is written 1430 and spoken as fourteen thirty hours.
Converting in your head is one rule plus two special cases. From 1:00 pm onwards, add 12 to the hours; morning times from 1:00 am to 12:59 pm keep their numbers. The special cases are the twelves: 12-something am (the midnight hour) becomes 00-something, and 12-something pm (the lunchtime hour) stays 12-something. Going the other way, subtract 12 from any hour of 13 or more, and read 00 as 12 am.
Worked examples
Full reference table
- 0000 = 12:00 am (midnight)
- 0100 = 1:00 am
- 0200 = 2:00 am
- 0300 = 3:00 am
- 0400 = 4:00 am
- 0500 = 5:00 am
- 0600 = 6:00 am
- 0700 = 7:00 am
- 0800 = 8:00 am
- 0900 = 9:00 am
- 1000 = 10:00 am
- 1100 = 11:00 am
- 1200 = 12:00 pm (noon)
- 1300 = 1:00 pm
- 1400 = 2:00 pm
- 1500 = 3:00 pm
- 1600 = 4:00 pm
- 1700 = 5:00 pm
- 1800 = 6:00 pm
- 1900 = 7:00 pm
- 2000 = 8:00 pm
- 2100 = 9:00 pm
- 2200 = 10:00 pm
- 2300 = 11:00 pm
Midnight, noon and the 12 o'clock problem
The 12-hour clock has one genuinely confusing spot: the twelves. Noon is 12:00 pm and midnight is 12:00 am, which trips people up because 12 pm feels like it should be night. The way to remember it is that am covers midnight up to just before noon, so midnight, as the first moment of the morning block, takes am. Even so, "12 am Friday" is ambiguous enough in practice (which end of Friday?) that careful writers say midnight or noon instead, or give times like 11:59 pm or 12:01 am on invitations and deadlines.
The 24-hour clock exists to remove exactly this ambiguity, which is why it is standard wherever a misread time is expensive: the armed forces, hospitals and medication charts, aviation, railway timetables and emergency services. Midnight is written 0000 as the start of a day, though you will occasionally meet 2400 used to mark the same instant as the end of the previous day. In Britain the two systems coexist comfortably: phones, timetables and ovens display 24-hour time while nearly everyone still says "half two" out loud, so converting between them is a daily habit rather than a military speciality.
If you are working out durations rather than clock formats, the hours calculator turns a start and finish time into hours worked, the time calculator adds and subtracts durations, and the time zone converter handles what 1430 in London becomes elsewhere. Turning hours worked into money is the hourly wage to salary converter's job.
Frequently asked questions
What is 1430 in normal time?
2:30 pm. For any 24-hour time from 13:00 to 23:59, subtract 12 from the hours and add pm. So 1430 becomes 2:30, and because 14 is past midday it is 2:30 in the afternoon.
Is midnight 12 am or 12 pm?
Midnight is 12 am and noon is 12 pm. A memory aid: am runs from midnight to just before noon, so the very first moment of the morning block, midnight, takes the am label. The 24-hour clock avoids the confusion entirely by writing midnight as 00:00 and noon as 12:00.
Is midnight 0000 or 2400 in military time?
Both appear, and they name the same instant. 0000 treats midnight as the start of the new day, which is the normal convention, while 2400 is occasionally used to mark midnight as the end of the previous day, for example when a document says a deadline of 2400 on Friday. Timetables and digital systems almost always use 0000.
How do you say military times out loud?
Read the hours and minutes as numbers: 0600 is spoken as zero six hundred (or oh six hundred), 1430 as fourteen thirty, and 2115 as twenty-one fifteen. The word hours is often added at the end, as in fourteen thirty hours. Leading zeros are always spoken.
Who uses the 24-hour clock?
Most of the world, for anything where am and pm could be misread: the armed forces, hospitals, airlines, railways and emergency services all use it, and most of continental Europe uses it in everyday writing. In the UK it is standard on timetables and digital devices even though people still say times aloud in 12-hour form.