You are researching Incandescent Lighting. Which iirc, is an Industrial era Tech. You are providing the Tech to the Barbs. Just because you are at calendar date 6639BC Means NOTHING using Pit's UEM. The Dates will Never match using a 20,000 turn Game Speed, Never. Why? Because the system of dating used is Badly flawed! More elegant my rearend! Made way too simple and therefore can never be even close in terms of Dating.. # of turns is more important than Date or Era in a 20,000 turn Game.
Forget the Date! The Tech is THE Most important factor.
How close are the other AI in terms of technology to yours? That is the key.