On futher looking it was only 1 century of difference in the 20th century (but probably more, earlier) in my 2 human players game, but I must say that RFC has been as close to real dates as possible from what I have seen in SP, so 1 century is indeed quite a difference since the last century lasts many, many turns. We started playing a 3000 BC start and we'll try also the 600 AD to check if it's all the same and hence due to more than one human player influencing the game, or if there's something odd in the 800 BC start.