Bad luck comes knocking around on doors again this year on Friday, July 13.
In 2018, the unlucky day falls on two separate dates – April 13 and July 13.
Friday the 13th is deeply ingrained in popular culture as a day of extreme misfortune and superstitious worries.
The fear of Friday the 13th even comes with a very lengthy name of its own – paraskavedekatriaphobia
But there is actually little consensus on why exactly Friday the 13th is considered to be an unlucky day.
Some of the superstition surrounding the date appears to be linked to Christian belief.
Jesus Christ is believed to have died on a Friday and 13 people attended his Last Supper, one of which sealed Jesus’ fate with the Romans.
Rebecca Borah, associate professor at McMicken College of Arts and Sciences, said: “The pre-Christian societies often noted the number 12 as representing completeness due to lunar cycles.
“So, 13 was a stepchild of a number.
Friday the 13: The infamous date is considered to be unlucky, but why?
“Later, a Christian overlay was added since the 13th apostle was Judas Iscariot.”
And if the Bible is anything to go by, some Christian traditions hold Eve tempted Adam with the forbidden fruit on a Friday and Cain slew his brother Abel on Friday 13.
The Christianity motif repeats itself on Friday, October 13, 1307, when French King Philip IV is said to have arrested hundreds of Knights Templar for crimes against God.
But the link is tenuous at best and the Knights Templar story was widely popularised by Dan Brown’s bestselling novel The Da Vinci Code.
Another theory suggests the date was associated with bad luck thanks to the 1907 novel by Thomas William Lawson, titled “Friday, the thirteenth”.
A Christian overlay was added since the 13th apostle was Judas Iscariot
The novel penned by the British stockbroker detailed a rogue businessman’s attempt to crash the stock market on Friday 13.
But other historians argue the numerical symbolism of the unlucky day goes even further back in time to Norse mythology.
According to Norse belief, the 12 gods of the Viking pantheon were rudely disturbed by a 13th unwelcome visitor during a dinner in Valhalla – the trickster god Loki.
Legend has it Loki tricked the god Hoor to shoot his brother Baldr with a lethal mistletoe-tipped arrow, thus branding the number 13 unlucky.
Friday the 13: Some think the date is linked to the arrest of Knights Templar in 1307
But the theories do not stop there and even mathematicians have had a go at cracking the Friday the 13th mystery.
Thomas Fernsler, from the University of Delaware, argued the number 13 is simply an uncomfortable one to deal with.
The lecturer said 12 is considered a “complete number” and 13’s connection to feelings of bad luck “has to do with it just being a little beyond completeness”.
Dr Fernsler said: “The number becomes restless or squirmy”.
Friday the 13th: Cain supposedly murdered his brother on this day
Whatever the historical and cultural root of Friday the 13th is the date has become a significant superstition in the Western world to the point where a series of slasher horror films were named after it.
Incident statistics do not support any irrational fears of increased misfortune on the day.
Igor Radun of Helsinki’s Institute of Behavioural Sciences, said in 2012: “No data exists, and will never exist, to confirm that the number 13 is an unlucky number.
“There is no reason to believe that any number would be lucky or unlucky.”