21:31 on a 24-hour clock is is 9:31 PM on a 12-hour clock. This system is used throughout the world (not just the military) and leverages a 24-hour time clock rather than the 12-hour AM/PM system known to most English speaking countries. Below are ways to convert 21:31 through a time chart, automated converter, and how to convert the 24 hour clock into a 12-hour AM/PM system by hand.
|24-hour format||12-hour format|
24-hour time is used in aviation, military, meteorology, logistics, and other fields. The 12-hour clock is only used in 18 countries globally, including the United States and Canada.
|24 Hour Clock||12 Hour Clock (AM/PM)||Military Time|
It is easy to convert from 24-hour time to 12-hour time once you know a few tricks. The primary difference between the two is that the hours in a 24 hour clock go all the way up to 23 (from 0 to 23). In a 12-hour clock, the hour resets to 1 after noon (midday). Follow the steps below to convert 21:31 to 12-hour time.
24-hour time and military time are very similar! See our page on military time for more information.