In this list, we’re taking a quick trip through ten of the unluckiest days different cultures side-eye, avoid, or treat with extra caution. Related: Ten Bizarre Facts About The Doge Meme10 Italy: Friday the 17thWhy Is 17 An Unlucky Number In Italy? You might even spot “missing” numbers in hotels or on planes, because some places avoid 17 the way Americans avoid 13. Add the number 13, which is long linked to chaos and bad breaks across the Christian tradition for much of the world, and you get a superstition combo meal. [9]1 United States: Friday the 13thWhy Are We Afraid of Friday the 13th and the Number 13?