How Do We Know The Earth Is 4.5 Billion Years Old? The 6,000 year age was arrived at by James Ussher, a 17th century Irish Archbishop who counted up estimates of the ages of Abraham’s family listed in the Old Testament and calculated that the creation began (on the Julian calendar) on Saturday, October 22, 4004 BC, at 6 pm. Really. Usher made a lot of assumptions, chose to ignore inconsistencies within even those scriptural sources known at that time, and was unaware of certain, now obvious translation issues, importantly including the way the Babylonians counted, but that’s beside the point. As William Henry Green wrote, “The Scriptures furnish no data for a chronological computation prior to the life of Abraham; and the Mosaic records do not fix and were not intended to fix the precise date either of the Flood or of the creation of the world.” In other words, even if Ussher’s calculation were correct (it isn’t) it would only tell us when Abraham lived, not when the world was made.