Chronos Guide

24-Hour Clock Guide

The 24-hour clock writes the day from 00:00 to 23:59. It is common in transport, medicine, computing and many countries outside the United States.

How to convert

Midnight is 00:00. Noon is 12:00. For PM times after noon, add 12 to the hour: 3:30 PM becomes 15:30, and 9:05 PM becomes 21:05.

Why it helps

The 24-hour clock removes AM/PM ambiguity. That is especially useful for flights, international calls, alarms and server maintenance windows.

Quick examples

7:00 AM is 07:00. 12:00 PM is 12:00. 6:45 PM is 18:45. 12:00 AM is 00:00.