(Photo credit: RT)
On September 26th, 1983, the world was nearly destroyed by nuclear war. That day is Petrov Day, named for the man who averted it. Petrov Day is a yearly event on September 26, commemorating the anniversary of the Petrov incident. It consists of an approximately one-hour long ritual with readings and symbolic actions with candles and other props.
The purpose of the ritual is to make catastrophic and existential risk emotionally salient, by putting it into historical context and providing positive and negative examples of how it has been handled. It is aimed primarily at those who already know what catastrophic and existential risks are, have some background knowledge about them, and believe (at least abstractly) that preventing those risks from coming to pass is important.
Petrov Day is designed for groups of 5-10 people, and consists of a series of readings and symbolic actions which people take turns doing. It is easy to organize; you'll need a few simple props (candles and a candle-holder) and a printout of the program for each person, but other than that no preparation is necessary.