1230 Military Time

1230 is half past noon, 12:30 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 exactly 12, which stays 12 and takes PM. This is the only PM hour where nothing is subtracted.

Noon. The one hour where the two systems share digits: 12:00 PM and 1200 look alike, and 1230 is 12:30 PM, not 12:30 AM. Nothing is added or subtracted here.

1230 sits 12.5 hours after midnight. A standard eight-hour shift that starts at 1230 ends at 2030; a twelve-hour shift ends at 0030 the next day.

Every single minute of this hour is listed on the 1200 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 1230 that lasts eight hours ends at 2030. For a shift with a break, the work hours calculator does the subtraction and accepts both formats.

Military to 12-hour. The hour is exactly 12, which stays 12 and takes PM. This is the only PM hour where nothing is subtracted. Keep the 30 minutes: 1230 is 12:30 PM.

12-hour to military. 12 PM keeps the 12. Noon is 1200 and 12:45 PM is 1245; only the AM hour after midnight changes to 00. So 12:30 PM is 1230: no colon, no PM, four digits.

The common slip is writing “12:30 PM”, which mixes the two systems. 1230 is half past noon; half past midnight is 0030.

1230 is said “twelve thirty”. With minutes attached, the word “hundred” disappears; “twelve hundred thirty” is wrong, and so is “twelve thirty hundred”. It is the same words you would use for the number 12 followed by the number thirty.

Minutes follow the same logic. 1205 is “twelve zero five” and 1240 is “twelve forty”. Single-digit minutes get a spoken zero, so the listener knows a digit is there.

About the word “hours”: in speech, “twelve 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 1230”, not “at 1230 hours”.

On its own, 1230 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 1230Z 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.