Did you know that AM stands for “ante meridiem” which means before noon in Latin? What about the fact that PM stands for “post meridiem” which means after noon in Latin? 

 

They are called post and ante meridiem because theanalog clock we currently use in the modern world is divided into two 12-hour increments. 

 

Why Do AM and PM Exist? 

 

The clocks we use today divide the day into two 12-hour time increments. This is because there are a total of 24 hours in a single day, which can be further split into two 12-hour periods. This is odd, considering when you look at clocks, they only display enough time to account for one of the two 12-hour periods. 

 

To remedy that problem, the two separate periods can be shown on the same analog clock by using the AM and PM suffixes.  

 

As we said above, AM stands for “ante meridiem” or before noon in Latin, so it is used to describe the first portion of the day – the first 12 hours. On the other hand, PM stands for “post meridiem” or after noon in Latin and it’s used to describe the second portion of the day – the final 12 hours. 

 

That’s why time is labeled with the AM or PM suffix; so that we can identify which portion of the day the time reference belongs to, but you probably already knew that part. 

 

This rule gets a bit confusing when you take a look at 12PM and 12AM respectively. For example, 12AM - or ante meridiem - does not make logical sense when you look at the rule because it does not actually come after midnight. 

 

Therefore, it is always better to refer to 12PM as noon and 12AM as midnight respectively even if analog and digital clocks do label them as the former.

 

Related Articles:

Where Does the 24 Hour Clock Format Come from?

What is DST?