97,445 BCE

The date 100,000 B.C.E. is the approximate time when The Forerunners fired the Halos, what the Covenant refer to as The Great Journey. The precise activation date was during 97,448 B.C.E., and it was meant to end the Forerunner-Flood War. The activation killed all sentient life in three radii of the galactic center including, it is believed, the Forerunners themselves. The date, about 100,000 years ago, is around the time our Homo Sapien ancestors began migrating out of Africa. It is when the Halo 3: The Cradle of Life comics take place.