To anyone thinking it's bad luck to set up the Christmas tree before December 24, that only applies if you use candles or lights that can get very hot. If you set the natural tree up too early and allow it to dry up, the needles can catch fire and burn your house down. I would say that would count as "bad luck".
You do not need to worry about that if you use LED lights (they are extremely cool burning), ultra miniature lights (they do not get hot enough to start a fire, but they can get warm), or an artificial tree. You can also prevent this "bad luck" if you keep the tree cool and watered, so the needles cannot dry out. Just one reminder: Unless your tree is one of those Norfolk Island pines that is in the pot, you cannot leave a cut tree up all summer long like you can an artificial tree.