In my game, in the 1st year Winter 2nd, the mayor said that he lost a bet to another mayor and he'll ask for a golden egg, turn your game off and start the day again, he'll ask for something different, keep doing it until he asks for black grass. Go to the Lake Mine (the one in the middle of a lake, the water is frozen so you can get to it) and use your hoe to plow around in the mine. It doesn't matter what level you plow at. You will
get black grass or bags with yellow stuff in it, that's money, but only 10G. At 7 pm, the mayor will come so give him the black grass and he will give you golden lumber but I don't know what to do with it.