The Anti-Monitor Crisis, the World Wide Crisis, the Crisis of Infinite Worlds, or simply the Crisis and also known as the Crisis of 2390, was a massive, apocalyptic event that encompassed the cataclysmic destruction of every single Earth in the multiverse by the Anti-Monitor's wave of antimatter, leaving only the chosen Paragons as the last survivors.
In the original timeline, the Crisis took place on the night of April 25, 2398, where both the Flash and his nemesis Reverse-Flash traveled back in time to March 18, 2371 to create the Flash, resulting in a temporal loop.
Due to changes in the timeline, the crisis occurred much earlier, on December 10, 2390.