Friday the 13th
This is an odd yet powerful belief that an entire day is unlucky. It seems to come from the two parts of it being both unlucky, the friday and the number 13. Although fridays are often seen as good now because they end the working week they used to be seen as bad, trying to complete or start anything on a friday was supposed to fail. The number however has ties to religion such as the twelve apostles, the twelve ancient Greek gods, and the twelve successors of Muhammad along with an ancient Norse myth of more than twelve people at a table invited death. This combined with other things such as twelve hours in time and twelve months in a year made the number twelve seen as a good whole number and anything more was unbalanced. The fear of the number is now so great it has even become unlucky in countries where it used to be lucky. There is a psychological reasoning that because people are thinking about bad things happening on this day they will notice the unlucky things more and take note of them more. However the fear of this day makes many people go out of their way somehow, some even refuse to leave their bed.