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. Guilty Spark stated that the time was exactly 101,217 years, but since he was measuring in local years, this may not be accurate for the human calendar. The activation killed all sentient life in three radii of the galactic center including the Forerunners themselves. The date, 100,000 years ago, is around the time our Homo sapiens ancestors decided to migrate out of Africa.

This is also the time period whete the Halo 3: The Cradle of Life mini comics takes place. This comics tells us that human peoples saw something ( the Ark ? ) being build by "Gods" ( Forerunner's machines ?) in Africa.