2100 hours = 9:00 PM
2100 hours is 9:00 PM in standard 12-hour time. On a 24-hour clock it is 21:00. Spoken military time is “twenty-one hundred hours”.
How to convert 2100
2100 is after noon. Subtract 12 from the hour (21 − 12 = 9) and add PM. The result is 9:00 PM. Hours 1300–2359 are all PM.