42 years ago today, lieutenant colonel Stanislav Petrov chose not to launch missiles against the United States while on duty in the Serpukhov-15 missile bunker after receiving what he correctly judged to be a false alarm in a early warning system.

This hasn't been formalized into a holiday so you'll find different advice online about how to celebrate, but I intend to raise a toast to Petrov and to watch the movie WarGames released the same year.