It is illegal to leave your Christmas decorations up after January 14th.

The Law Explained

In a state that experiences long and brutal winters, leaving holiday lights up might seem like a nice way to beat the seasonal depression. However, an old regulatory concept dictates that festive decorations become a public nuisance if left up well into the new year. It was originally intended to keep neighborhoods looking tidy and to prevent aging electrical wires from becoming fire hazards.