A Quick Guide to Converting AM/PM Time to 24 Hour Format

First, there is the 12 hour clock that uses AM and PM, and then there is the 24 hour clock.

In Latin America and English-speaking countries, the 12 hour clock method is widely used. In the 12 hour clock method, 12:00 is twice a day at midnight (AM) and noon (PM).

The table below shows the conversion between the 12 hour and 24 hour clock systems:

12 Hour Clock

During the day, there are two 12-hour periods: midnight to noon (AM hours), and noon to midnight (PM hours).

The abbreviations AM and PM are from Latin:

• AM: ante meridiem, before midday
• PM: post meridiem, after midday

24 Hour Clock

Day runs from midnight to midnight and is divided into 24 hours from 0 (midnight) to 23. Time is given in hours and minutes since midnight.

Changing a 12 hour clock to a 24 hour clock

Starting from the first hour of the day (12:00 AM or midnight to 12:59 AM), subtract 12 hours:

• 12:00 AM = 0:00
• 12:15 AM = 0:15

From 1:00 AM to 12:59 PM, the hours and minutes remain the same:

• 9:00 AM = 9:00
• 12:59 PM = 12:59

For times between 1:00 PM to 11:59 PM, add 12 hours:

• 3:17 PM = 15:17
• 11:59 PM = 23:59

Changing a 24 hour clock to a 12 hour clock

Starting from the first hour of the day (0:00 / midnight to 0:59), add 12 hours and AM to the time:

• 0:30 = 12:30 AM
• 0:55 = 12:55 AM

Add AM to the time from 1:00 to 11:59:

• 2:25 = 2:25 AM
• 9:30 = 9:30 AM

Add PM to the time between 12:00 and 12:59:

• 12:15 = 12:15 PM
• 12:48 = 12:48 PM

Subtract 12 hours from the time and add PM for times between 13:00 and 23:59:

• 16:55 = 4:55 PM
• 21:45 = 9:45 PM

TechVipGroup’s open source curriculum has helped more than 60,000 people find jobs as developers.