1800 Military Time

1800 is 6:00 PM, six o’clock in the evening. On a 24-hour clock with a colon it is 18:00; in military style the colon goes and the four digits stand alone. The hour is 18 hours after midnight and 6 hours before the next one.

Six in the evening. 1800 is dinner on most installations and the start of many second shifts.

To read it, look at the first two digits: the hour is above 12, so subtract 12 and add PM: 18 − 12 = 6. The last two digits are minutes and never change, so 1825 is 6:25 PM and 1850 is 6:50 PM.

Military to 12-hour. Split the four digits into hours and minutes, the hour is above 12, so subtract 12 and add PM: 18 − 12 = 6. So 1815 becomes 6:15 PM and 1845 becomes 6:45 PM.

12-hour to military. 6 PM is a PM hour, so add 12: 6 + 12 = 18. 6:05 PM is 1805. Drop the colon and the AM or PM, and you have the four digits.

The mistakes worth knowing: “18:00 PM” is a mix of both systems and means nothing, because a 24-hour time already says which half of the day it is. And 1800 is not 18:00 AM; there is no 18 o’clock in the morning.

1800 is said “eighteen hundred”. The “hundred” stands in for the two zeros; nobody says “thirteen zero zero”. Numbers from ten upward are said as ordinary numbers: “eighteen hundred”, not “one eight hundred”.

Minutes follow the same logic. 1805 is “eighteen zero five” and 1840 is “eighteen forty”. Single-digit minutes get a spoken zero, so the listener knows a digit is there.

About the word “hours”: in speech, “eighteen 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 1800”, not “at 1800 hours”.

On its own, 1800 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 1800Z 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.