Noon and Midnight
Which one is AM or and which is PM?
Common convention says that “12:00 AM” is midnight, and “12:00 PM” is noon. But this is technically not official.
AM refers to the period after midnight and before noon, and PM refers to the period after noon and before midnight. Therefore, these times are neither AM nor PM, and the style of “12:00 AM” or “12:00 PM” are incorrect.
Several style guides – including AP Style and Chicago Style – prohibit the usage of “12:00” for precisely this reason. They mandate “noon” and “midnight.”
In military time, midnight is “2400” or “twenty four hundred.”
Why I Looked It Up
I was trying to schedule a meeting for noon, and the dropdown had “12:00 p.m. listed. I didn’t know if that was the time I wanted, or 12 hours from the time I wanted. (According to convention, this was noon.)