How is midnight handled?

12:00 AM is midnight and converts to 00:00 in 24-hour format. In the other direction, 00:00 through 00:59 convert to 12:00 AM through 12:59 AM, since the hour zero is the 12 oclock hour after midnight.

12:00 PM is noon and stays as 12:00 in 24-hour format. The hours 12:00 through 12:59 in 24-hour time convert to 12:00 PM through 12:59 PM, the only PM hour that keeps the number 12.

Do I have to type a colon?

No. The tool accepts a compact form without a colon, so 1434 is read the same as 14:34 and 230 PM the same as 2:30 PM. This makes pasting from logs or schedules easier.

What counts as invalid input?

A 24-hour time with an hour above 23 or minutes above 59 is rejected, as is a 12-hour time with an hour outside 1 to 12 or a missing AM/PM marker. Invalid input shows an error instead of a wrong answer.

Why use 24-hour time at all?

The 24-hour clock removes any ambiguity about morning versus evening, which is why it is standard in aviation, the military, healthcare, and most of the world outside the United States. It also sorts and compares more easily in software.

12-Hour and 24-Hour Time Converter

This converter switches clock times between the 12-hour AM/PM format common in the United States and the 24-hour format used in most of the world and in any context where ambiguity is unacceptable. It works in both directions and gets the tricky midnight and noon cases right.

How it works

Converting from 12-hour to 24-hour applies two rules to the hour, leaving the minutes untouched:

if period is AM and hour == 12  ->  hour = 0
if period is PM and hour != 12  ->  hour = hour + 12

Converting from 24-hour back to 12-hour reverses this: the period is AM when the hour is below 12 and PM otherwise, and the displayed hour is hour mod 12, shown as 12 when that result is zero. The minute field is always two digits.

Example and tips

2:34 PM becomes 14:34, while 00:15 becomes 12:15 AM. The two cases worth memorising are the boundaries: midnight is 12:00 AM equal to 00:00, and noon is 12:00 PM equal to 12:00. If you are storing times in software, prefer the 24-hour form because it sorts correctly as text and avoids the AM/PM ambiguity entirely.