A tutorial of a fake time system (like yours). I even managed to find a way to make the time won't pass when you have some menu open!
The error is because Time class limitations that use a Long object to hold the seconds, so it can't convert to a Bignum, in other words, the year can only be in range 1970-2037. In my system I am developing how to handle when the year pass this range to won't crash the game.