0900 Military Time

0900 is 9:00 AM, nine o’clock in the morning. On a 24-hour clock with a colon it is 09:00; in military style the colon goes and the four digits stand alone. The hour is 9 hours after midnight and 15 hours before the next one.

Nine in the morning, the last single-digit hour and therefore the last one that carries a leading zero.

To read it, look at the first two digits: the hour is below 12, so drop the leading zero and add AM: 9 o’clock in the morning. The last two digits are minutes and never change, so 0925 is 9:25 AM and 0950 is 9:50 AM.

Military to 12-hour. Split the four digits into hours and minutes, the hour is below 12, so drop the leading zero and add AM: 9 o’clock in the morning. So 0915 becomes 9:15 AM and 0945 becomes 9:45 AM.

12-hour to military. 9 AM keeps its number and gains a leading zero so that it has four digits: 9:05 AM is 0905. Drop the colon and the AM or PM, and you have the four digits.

The mistakes worth knowing: “09:00 AM” is a mix of both systems and means nothing, because a 24-hour time already says which half of the day it is. And 0900 is not 9 PM; 9 PM is 2100.

0900 is said “zero nine hundred”. The “hundred” stands in for the two zeros; nobody says “thirteen zero zero”. The leading zero is spoken: “zero nine hundred”. “Oh nine hundred” is common in conversation and in films, but “zero” is what radio procedure and most instructors use, because “oh” can be misheard.

Minutes follow the same logic. 0905 is “zero nine zero five” and 0940 is “zero nine forty”. Single-digit minutes get a spoken zero, so the listener knows a digit is there.

About the word “hours”: in speech, “zero nine hundred hours” is everywhere, and nobody will correct you. In writing, Army Regulation 25-50 says the word is not used with military time, so a memorandum reads “at 0900”, not “at 0900 hours”.

On its own, 0900 is local time wherever it is written. When the four digits carry a letter, the letter is the time zone. Z stands for Zulu, which is UTC, and J (Juliet) means the local time of the person speaking. The table converts 0900Z to the four US zones, in standard time and in daylight saving time.

Eastern Time is four hours behind UTC from March to November and five hours behind the rest of the year, which is why one Zulu time maps to two possible local times. The other three zones follow the same pattern an hour further west each.

Midnight has a second spelling, 2400, used when it marks the end of a day rather than the start. The full rules, with a converter, are on the military time chart page.