Military time (24-hour clock)

Military time conversion chart

How to read and say military time

The rule is simple: from 1:00 PM onward, add 12 to the hour. 1830 is 18 − 12 = 6:30 PM; 2145 is 9:45 PM. Before 1:00 PM the numbers match the ordinary clock, written with four digits — 9:05 AM is 0905.

Whole hours are spoken with "hundred": 0600 is "zero six hundred" and 1800 is "eighteen hundred". Times with minutes are read digit by digit or as a pair — 1830 is "eighteen thirty". Midnight is written 0000 ("zero hundred"); the same instant at the end of a day is sometimes written 2400 on schedules that need a closing time.

Going the other way, convert an afternoon or evening 12-hour time by adding 12: 6:30 PM becomes 1830, 11:15 PM becomes 2315.

Zulu time and who uses the 24-hour clock

Military messages often add a letter to mark the time zone. "Z" — Zulu in the NATO phonetic alphabet — means UTC, so "1500Z" is 3:00 PM UTC regardless of where the sender is. Local zone letters exist too (Romeo is UTC−5, for example), but Zulu is by far the most common because it lets units in different zones share one unambiguous clock.

Beyond the US military, the 24-hour clock is standard in aviation (flight plans and METAR weather reports are filed in Zulu), in hospitals and emergency services where an AM/PM mix-up could be dangerous, on transit timetables, and in everyday life across most of the world outside North America.