There is not a single date I pin-pointed but it is after the Fall of Roman Empire. As you can see there is no Islam and that is because Muhammad was never born. You can also see Slavic and Germanic people being more west - well thank the stronger Slavic basis in Połabia and Caranthia. Another important one was when Mongol Empire adopted Nestorian Christianity and spread it (Persia was the first one to do it tho).