What's the Difference A.M. and P.M.?

Key Differences Between AM and PM

Feature	AM	PM
Meaning	Ante Meridiem – before noon	Post Meridiem – after noon
Time Range	12:00 midnight to 11:59 AM	12:00 noon to 11:59 PM
Associated Part of Day	Morning	Afternoon and evening
Examples	7:00 AM – early morning	7:00 PM – evening
Usage Tip	Use AM for times before noon	Use PM for times after noon

Conclusion: Remember, AM is before noon, and PM is after noon. This simple distinction helps in scheduling and avoiding confusion when using the 12-hour clock.

AM (Ante Meridiem)

Latin for “before midday”
Refers to the time from midnight to noon
12:00 AM is midnight
Times from 12:00 AM to 11:59 AM
Associated with morning hours
Example: 9:00 AM is 9 in the morning

PM (Post Meridiem)

Latin for “after midday”
Refers to the time from noon to midnight
12:00 PM is noon
Times from 12:00 PM to 11:59 PM
Associated with afternoon and evening hours
Example: 3:00 PM is 3 in the afternoon

Common Examples

12:00 AM

Midnight (start of the day)

6:00 AM

Early morning

12:00 PM

Noon (midday)

3:00 PM

Afternoon

6:00 PM

Evening

11:59 PM

One minute before midnight

Historical Background

The 12-hour clock system dates back to ancient Egypt and Mesopotamia. These civilizations used sundials during the day and water clocks at night, dividing both periods into 12 hours each.

The terms “AM” and “PM” come from Latin:

AM = Ante Meridiem (before midday)
PM = Post Meridiem (after midday)

This system became widely used with the invention of mechanical clocks in Europe during the 14th century and remains popular in many English-speaking countries today.

12-Hour to 24-Hour Conversion

Many countries use the 24-hour clock system (military time). Here’s how to convert between the two:

12:00 AM