Unlucky Day is observed on December 31, 2017. It takes place on the last day of the year and will be unlucky for some people. The das is a chance to get unlucky things out of the way, so you can start the next year with good luck.
Luck or chance is an event which occurs beyond one's control, without regard to one's will, intention, or desired result. Cultural views of luck vary from perceiving luck as a matter of random chance to attributing to such explanations of faith or superstition. (With material from: Wikipedia)