Being wary of Friday the 13th is much more than a quaint superstition observed by a few uneducated people in distant, unreachable towns and hamlets. In the United States alone, it is estimated that between 17 and 21 million people dread that date to the extent that it can be officially classified as a phobia.
So why is Friday the 13th considered such an “evil” day?
The origins aren’t perfectly clear, but we do know that both Friday and, separately, the number 13 have long been considered unlucky and it was around the late 19th century that the first documented instances started popping up of people putting the two together to form the unluckiest day of all.
To start with, the most popular theory as to why Friday is considered unlucky or an evil day is thought by many to spring from Christianity. By tradition, Friday is considered the day that Eve gave Adam the “apple” and they were kicked out of the Garden of Eden- of course, “Friday” wouldn’t have been around yet.
(Note: The notion that it was an apple is a second century invention and contrary to what is stated in Genesis.)
Also by tradition, Adam and Eve were purported to have died on a the then nonexistent “Friday”. The Temple of Solomon was said to have been destroyed on Friday. And Jesus was traditionally considered to have been crucified on a Friday, the day we refer to now as Good Friday. Though, interestingly, there are several references in somewhat recent history of Good Friday being considered the one exception to Fridays being bad luck. Such as this reference from 1857:
For the rest of the story: http://gizmodo.com/why-people-think-friday-the-13th-is-unlucky-1306401570