The 24-hour clock — called military time in the US — counts the hours of the day from 00:00 to 23:59, with no AM or PM. It's the standard in most of the world and in aviation, medicine, and the military. Here's how it works and how to convert.
For the current time anywhere, see the world clock.
How the 24-hour clock works
Instead of restarting at 12 after noon, the hours keep counting up:
- The day starts at 00:00 (midnight).
- Noon is 12:00.
- The afternoon and evening continue 13:00, 14:00 … 23:00.
- The last minute of the day is 23:59, then it rolls to 00:00.
Because each time is unique, there's no AM/PM ambiguity — a big reason it's used where mistakes matter.
Converting 12-hour to 24-hour
- AM hours are the same, except 12 AM (midnight) = 00:00.
- PM hours: add 12, except 12 PM (noon) stays 12:00.
| 12-hour | 24-hour |
|---|---|
| 12:00 AM | 00:00 |
| 6:00 AM | 06:00 |
| 12:00 PM | 12:00 |
| 1:00 PM | 13:00 |
| 5:00 PM | 17:00 |
| 9:00 PM | 21:00 |
| 11:00 PM | 23:00 |
Converting 24-hour to 12-hour
- 00:xx → 12:xx AM
- 01:00–11:59 → same numbers, AM
- 12:00–12:59 → same numbers, PM
- 13:00–23:59 → subtract 12, PM (e.g. 18:30 → 6:30 PM)
"Military time" quirks
In US military usage, times are often written without a colon and spoken in hundreds — 0900 = "zero nine hundred," 1700 = "seventeen hundred." Midnight is 0000 ("zero hundred").
Quick answers
What is the 24-hour clock? A timekeeping system where hours run 00:00 to 23:59 with no AM/PM.
What is 1 PM in 24-hour time? 13:00.
How do I convert PM to 24-hour time? Add 12 to the hour, except 12 PM (noon) which stays 12:00.
What is midnight in 24-hour time? 00:00 (sometimes written 24:00 for the end of a day).