Friday the 13th : Explained.

What better day to unravel the mystery of Friday the 13th then Thursday the 13th? So here it goes, 13 is considered unlucky because 12 is considered such a complete number ie- 12 months of the year, 12 signs of the zodiac, 13 was considered to "transgress this completeness" so that's why 13 is considered unlucky. Friday is considered unlucky because it's commonly believed by them Christians that, that was the day that Jesus was crucified.
There's another piece of information for you to tell your friends. Faces will look like this: