1600 Military Time

1600 is 4:00 PM, four o’clock in the afternoon. On a 24-hour clock with a colon it is 16:00; in military style the colon goes and the four digits stand alone. The hour is 16 hours after midnight and 8 hours before the next one.

Four in the afternoon. Its half hour, 1630, is one of the most looked-up military times, because so many duty days end then.

To read it, look at the first two digits: the hour is above 12, so subtract 12 and add PM: 16 − 12 = 4. The last two digits are minutes and never change, so 1625 is 4:25 PM and 1650 is 4:50 PM.

Military to 12-hour. Split the four digits into hours and minutes, the hour is above 12, so subtract 12 and add PM: 16 − 12 = 4. So 1615 becomes 4:15 PM and 1645 becomes 4:45 PM.

12-hour to military. 4 PM is a PM hour, so add 12: 4 + 12 = 16. 4:05 PM is 1605. Drop the colon and the AM or PM, and you have the four digits.

The mistakes worth knowing: “16:00 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 1600 is not 16:00 AM; there is no 16 o’clock in the morning.

1600 is said “sixteen hundred”. The “hundred” stands in for the two zeros; nobody says “thirteen zero zero”. Numbers from ten upward are said as ordinary numbers: “sixteen hundred”, not “one six hundred”.

Minutes follow the same logic. 1605 is “sixteen zero five” and 1640 is “sixteen forty”. Single-digit minutes get a spoken zero, so the listener knows a digit is there.

About the word “hours”: in speech, “sixteen 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 1600”, not “at 1600 hours”.

On its own, 1600 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 1600Z 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.