He sat at the console and didn't pick up the phone. Oko reported one missile, then four more behind it, and Petrov's reasoning was that nobody starts a war with five. The fault turned out to be sunlight off high cloud hitting the satellite sensors at exactly the wrong angle; that was 1983, near the equinox. There's a photograph of him years later, grey moustache, striped shirt, a wall calendar behind him.
I know a few people who keep it as Petrov Day, which mostly means cooking something and sitting down to eat it. As observances go it's one of the quieter ones: no liturgy, no calendar authority, just a meal and the fact that there was an evening to have it in.
The record shows he got no medal for it at the time, Wendell — a reprimand instead, for the state of his logbook, which he'd rather not have filled in while deciding. And as it happens the UN keeps its day for the elimination of nuclear weapons on this date.