Today is Friday the 13th.
It's an unlucky day for many superstitious people, though researchers are not sure why.
Professors who study the origins of superstitions have found no mentions of Friday the 13th before the 19th century.
The superstition may have arisen in the Middle Ages, originating from the biblical story of the last supper where 13 individuals were present.
While there is evidence of both Friday and the number 13 being considered unlucky, there is no record of the two items being referred to as especially unlucky in conjunction.
It may comfort some music fans to know that 13 is Taylor Swift's lucky number.
The pop star says she was born on the 13th, turned 13 on Friday the 13th, and that her first album went gold in 13 weeks.
She even says her first number-one song had a 13-second intro.
"Every time I’ve won an award I’ve been seated in either the 13th seat, the 13th row, the 13th section or row M, which is the 13th letter,” Swift has said.
By the way ... the fear of Friday the 13th is known as Paraskivedekatriaphobia.