well since you can take control of a nation at about 1450 (ends in 1819)- and then get free hands - you can imagine how accurate it is (or should I say - becomes)!
but the different starting ages shows, quite accurately, where the nations had colonies and which kings were in charge etc. + somewhat accurate how their internal policies were..
and the entire world is available for you to conquer - at least what was discovered before 1819..