There are 12 months in a year, 12 inches in a foot, 12 signs of the Zodiac, and most multiplication tables go up to 12; and so one more of any of these would make 13. The modern day fear of 13 is based on Norse mythology: 12 gods were dining at Valhalla (where gods go when they die) when Loki (a trickster god) showed up. He caused the death of Baldr, god of light and joy.

From that day forward, 13 has been considered unlucky. Bibliophiles know that Adam and Eve were expelled from the Garden of Eden on a Friday, Noah’s Great flood started on a Friday, and Christ was crucified on a Friday. Christians have also noted that 12 witches plus one devil are present at satanic ceremonies – so Friday and 13 make a scary combination.