I think the dates are random. The point of these teasers is just that - to be teasers, not to actually give us a way of figuring out anything exact. The only thing we "know" is that it will end on one particular year. So what we should do is think of a particular event of special importance to the possible areas it could be and see if any years stand out and we can guess that might be the one it ends on.
Because of the riddle - not Rome, not Shogun, no guns, BUT IS in the east if I interpreted it correctly - and naval warfare I personally I think it will revolve around China including warring dynasties and involve Japan, Korea, Mongolia, and India for diversity of factions and greater use of ships. I only know some general history from these places so I can't guess a year but I bet this is where to look.
Anyone know some significant dates in Chinese history? Maybe the Yellow Turban Rebellion or the rise of the Han?
EDIT: I bet it's "Dynasty: Total War". I'll be so happy if I'm right
