1630 Military Time

1630 is half past four in the afternoon, 4:30 PM. The first two digits are the hour, the last two are the minutes, and the minutes are the same in every system: 30 stays 30. Only the hour needs attention: the hour is above 12, so subtract 12 and add PM: 16 − 12 = 4.

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

1630 sits 16.5 hours after midnight. A standard eight-hour shift that starts at 1630 ends at 0030 the next day; a twelve-hour shift ends at 0430 the next day.

Every single minute of this hour is listed on the 1600 page.

Adding whole hours to military time is a plain sum until you pass 2359, then you subtract 24 and move to the next day. A shift from 1630 that lasts eight hours ends at 0030. For a shift with a break, the work hours calculator does the subtraction and accepts both formats.

Military to 12-hour. The hour is above 12, so subtract 12 and add PM: 16 − 12 = 4. Keep the 30 minutes: 1630 is 4:30 PM.

12-hour to military. 4 PM is a PM hour, so add 12: 4 + 12 = 16. 4:05 PM is 1605. So 4:30 PM is 1630: no colon, no PM, four digits.

The common slip is writing “16:30 PM”, which mixes the two systems. 1630 cannot be a morning time, because 16 is past 12; the morning equivalent would be 0430.

1630 is said “sixteen thirty”. With minutes attached, the word “hundred” disappears; “sixteen hundred thirty” is wrong, and so is “sixteen thirty hundred”. It is the same words you would use for the number 16 followed by the number thirty.

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 1630”, not “at 1630 hours”.

On its own, 1630 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 1630Z 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.