I'm not 100% sure this will work. It works with Gamehour so I assume it would with Gameyear as well. If you look at http://geck.gamesas.com/index.php/List_of_Global_Variables list you will see Gameyear as one. I think you can just say
set Gameyear to 2250
thus setting it to 2250. I don't know if it starts out as 0 for year 0 or what, but mess around with that line of code, as it should do what your looking for with a little tweaking.
Gunmaster95