The oldest written records in the Great Library of Orwen are from 20,000 years ago. They were written as the world was recovering from a great catastrophe. Even in these ancient records, the Cataclysm is referred to as something that happened generations before, so its exact date and the details of what happened are lost to time. The most involved description of the event is found in the Book of Aki:
And the sky boiled and was split apart by the searing heart of the heavens, and it was as if the Holy Seven themselves looked upon Ki’vun and scorned its people. The masses of the Chosen stood upon the shores and watched the Great Ocean Kingdom devoured by fire and steam. And in the gods’ next breath, even the Chosen were swallowed by the heat of the heavens. After the sky folded up, the lands were covered by a Great Flood for a millennium, and the survivors were bidden by the Holy Seven to begin anew.