Convert between 12-hour and 24-hour time
| 24-Hour | 12-Hour | Spoken | 24-Hour | 12-Hour | Spoken |
|---|---|---|---|---|---|
| 0000 | 12:00 AM | zero hundred | 1200 | 12:00 PM | twelve hundred |
| 0100 | 1:00 AM | zero one hundred | 1300 | 1:00 PM | thirteen hundred |
| 0200 | 2:00 AM | zero two hundred | 1400 | 2:00 PM | fourteen hundred |
| 0300 | 3:00 AM | zero three hundred | 1500 | 3:00 PM | fifteen hundred |
| 0400 | 4:00 AM | zero four hundred | 1600 | 4:00 PM | sixteen hundred |
| 0500 | 5:00 AM | zero five hundred | 1700 | 5:00 PM | seventeen hundred |
| 0600 | 6:00 AM | zero six hundred | 1800 | 6:00 PM | eighteen hundred |
| 0700 | 7:00 AM | zero seven hundred | 1900 | 7:00 PM | nineteen hundred |
| 0800 | 8:00 AM | zero eight hundred | 2000 | 8:00 PM | twenty hundred |
| 0900 | 9:00 AM | zero nine hundred | 2100 | 9:00 PM | twenty-one hundred |
| 1000 | 10:00 AM | ten hundred | 2200 | 10:00 PM | twenty-two hundred |
| 1100 | 11:00 AM | eleven hundred | 2300 | 11:00 PM | twenty-three hundred |
With minutes, say the hour then the minutes as two digits: 0930 is "zero nine thirty," 1445 is "fourteen forty-five." Minutes are identical in both systems; only the hour changes. Times before 10 AM keep a leading zero (0700, not 700).
Military time is the 24-hour clock: the day runs 0000 to 2359 with no AM or PM. The conversion is two rules and one exception pair, and the calculator applies them both directions while showing the spoken form and a live clock so you can sanity-check against your own watch.
12-to-24: for PM hours 1 through 11, military hour = hour + 12; for AM hours 1 through 11, military hour = hour; 12 AM maps to 00 and 12 PM maps to 12. Minutes pass through untouched. 24-to-12: hours 13 through 23 become hour − 12 with PM attached; hours 00 through 12 keep their number with AM (00 becomes 12 AM).
Pick a direction, type the time, and the result updates as you go. The spoken-form row shows how it's said over a radio or in a hospital, and the alternate notation shows the colon format (19:42) used by timetables outside the US. The live clock always shows your current local time in 24-hour form.
Convert 7:42 PM. The hour is 7, which is in the 1-to-11 PM range, so add 12: 7 + 12 = 19. Minutes stay 42. Result: 1942, spoken "nineteen forty-two," written 19:42 in colon form. Now go backwards from 0930: the hour 09 is below 12, so it stays 9 with AM attached, giving 9:30 AM, "zero nine thirty."
The only place people stumble is the 12s. Noon is 1200, not 0000, and midnight is 0000, not 1200. After midnight, 12:01 AM through 12:59 AM convert to 0001 through 0059, the lowest numbers on the clock.
Add 12 to the hour for any time from 1 PM to 11 PM, and keep the minutes unchanged. So 2:47 PM becomes 1447 and 7:15 PM becomes 1915. The two edge cases are midnight and noon: 12:00 AM becomes 0000 and 12:00 PM stays 1200. Morning hours from 1 AM to 11 AM keep their numbers, written with a leading zero, so 9:05 AM is 0905.
1700 is 5:00 PM. Hours from 13 to 23 in 24-hour time map to 1 PM through 11 PM by subtracting 12, so 1300 is 1 PM, 1500 is 3 PM, and 2300 is 11 PM. Minutes never change between the two systems.
Both appear, and they mean the same instant approached from different days. 0000 (zero hundred) is the start of a new day, which is what clocks and most writing use. 2400 marks the end of a day and shows up mainly in schedules that span midnight, like a shift that runs 2000 to 2400. The next minute after 2359 is 0000 of the following day.
Say the hours as a hundred, then the minutes as two digits. 0900 is zero nine hundred hours, 1200 is twelve hundred hours, and 1830 is eighteen thirty. Whole hours usually get the full treatment, zero nine hundred hours, while times with minutes often shorten to the number pairs: 1445 is fourteen forty-five.
The format is the same 24-hour clock, but Zulu time specifically means UTC, zero time-zone offset. Aviation and the military append Z to show a UTC timestamp, as in 1400Z. Local military time carries no letter, so 1400 local and 1400Z can be hours apart. Radio phonetics call Z "Zulu," which is where the nickname comes from.
Because it removes the AM/PM ambiguity that causes real harm. A chart order for 7:00 could mean morning or evening; 0700 and 1900 cannot be confused. The US military adopted it across alliances for the same reason, and it is the civilian standard through most of Europe and Latin America, where timetables simply say 14:30.