What do AM and PM mean in time notation?

[Atul]

I often see times written with AM and PM but I'm not sure what they stand for or how they work. Can someone explain the difference and when each is used?

 

[inzhenerna_jmpr]

AM means “Ante Meridiem,” Latin for “before midday.”
PM means “Post Meridiem,” Latin for “after midday.”


So, AM refers to the hours midnight to noon, and PM refers to noon to midnight.

 

[danisjohn]

AM and PM come from Latin. AM means ante meridiem (“before midday”), covering midnight to noon. PM means post meridiem (“after midday”), covering noon to midnight. They help distinguish morning from afternoon and night in the 12-hour clock format.