Updated

If you suffer from triskaidekaphobia, the 13th of every month is certainly not your day.

Triskaidekaphobia is the fear of the number 13. So, if you are a triskaidekaphobe and superstitious, Friday the 13th can be terrifying.

There’s a lot of folklore to buttress a triskaidekaphobe’s fear, and early examples date all the way back to the Bible.

FRIDAY THE 13TH ECLIPSE VISIBLE IN ANTARCTICA

Judas, the apostle known for betraying Jesus, is believed to be the 13th guest at the Last Supper. In addition, many people believe the Crucifixion of Jesus was on a Friday. Cain was also thought to have killed Abel on Friday the 13th.

In modern times, the horror film series "Friday the 13th" chronicles the activities of serial killer Jason Voorhees, his mother and their victims, of which there are many among the 12 movies.

The number 13 is the number of witches necessary to make a coven. There’s also the ill-fated Apollo 13 moon mission (although you can hear from an Apollo 13 astronaut recounting what actually went wrong on the fatal mission here).

FRIDAY THE 13TH HARVEST MOON THRILLS SKYWATCHERS

Numerologists say 12 is a "complete" number, which means 13 is not. There are 12 Zodiac signs, 12 months in a year, and 12 tribes of Israel. The number 13 simply doesn’t complete things as the number 12 does.

CLICK HERE TO GET THE FOX NEWS APP

Now, at least if you suffer from agoraphobia - the fear of certain places and situations - you'll know why days like today can be so frightening.

Emily DeCiccio is a video producer and writer for Fox Digital Originals. Follow her on Twitter @EmilyDeCiccio