By Johnny Caldwell
Friday is one of two occasions this year - the other being in July - when a Friday happens to be the 13th day of the month.
Black cats are often associated with superstitions
Interestingly, any month starting on a Sunday will have a Friday the 13th and each year will have at least one. People born on a Friday the 13th include Margaret Thatcher, Fidel Castro, zany actor Steve Buscemi and the Olsen twins, Mary-Kate and Ashley.
If you think this article is already a load of mumbo-jumbo, you may be surprised to learn that Belfast City Hall has no bookings for weddings this Friday the 13th on a day, given the time of year, when there could possibly be several.
But why does this combination of Friday and 13 prove such a talking point, let alone leave some so stricken with fear that they'll spend most of the day in bed?
Both 13 and Friday have their own legacies of bad luck associations which the superstitious among us believe combine to produce the unluckiest day of the year.
Much of 13's bad luck associations appear to be directly related to the fact that it comes immediately after 12.
Numerologists consider 12 to be a complete number.
There are 12 months in a year, 12 signs of the zodiac, and 24 hours in a day, a number which is evenly divisible by 12.
Thomas Fernsler of Mansfield University, Pennsylvania, says 13 is considered unlucky because by exceeding 12 by 1, it is "a little beyond completeness" and subsequently "restless or squirmy".
The number's association with bad luck also has a biblical reference.
Judas, the apostle who betrayed Jesus, was the 13th guest to the Last Supper.
In Norse mythology, 13's inauspiciousness is traced back to a dinner party at which 12 Norse gods were having a dinner party at Valhalla, their heaven.
The 13th guest was the mischievous Loki, who once there arranged for Hoder, the blind god of darkness to shoot Balder the Beautiful, the god of joy and gladness with a mistletoe-tipped arrow.
Balder died and the world was plunged into darkness.
Numerous more contemporary instances of people being afraid of the number 13 can also be found.
These are presumably linked to the aforementioned reasoning and events.
In France, socialites known as quatorziens (fourteeners) up until relatively recently made themselves available in case it would happen that a dinner party had 13 guests.
There are also numerous examples of sports teams playing without a number 13 shirt, and high-rise buildings such as hotels not having a floor number 13, which may be disguised or simply omitted.
Windsor House has a 13th floor, but many buildings do not
However, Belfast's tallest building, Windsor House, situated in the centre of Northern Ireland's capital, does not follow this trend, and anyone using its lift can stop at floor 13.
Any event or happening can of course add to the already sizeable legacy of bad luck associated with the number 13 - such as the ill-fated mission to the moon Apollo 13.
Reasons why Friday is considered to be an unlucky day are fewer and primarily related to significant events in Christianity.
It is believed, for example, that the crucifixion of Jesus took place on a Friday (Good Friday) as did Eve's offering of an apple to Adam in the Garden of Eden.
This day which heralds the start of the weekend is also said to have witnessed the start of the Great Flood and the confusion at the Tower of Babel.
There are also numerous literary references to Friday being unlucky, which date back to Chaucer's Canterbury Tales in the 14th century ("And on a Friday fell all this mischance").
In Britain as well as ancient Rome, Friday was once known as Hangman's Day because it was usually the day upon which those who had been condemned to death would be hanged.
While we may never know the exact origins of why the coming together of the number 13 and Friday can make us a little apprehensive, to say the least, does it really have that much of an impact in 2007?
Dr Arthur Cassidy, a psychologist at Belfast Institute, says although there is "no real empirical research on this", a fear of Friday the 13th could have a big impact on someone who has "a vulnerable personality and open to things such as astrology and a belief in fate".
"And if you took a random sample of 10 people from any town or city in Northern Ireland, there would probably be about two or three people who would do things differently because it is Friday the 13th," he says.
Friday the 13th related trivia
Paraskevidekatriaphobia is a fear of Friday the 13th while triskaidekaphobia is a fear of the number 13.
According to a British Medical Journal study there is a significant increase in traffic related accidents on Friday the 13th.
The Stress Management Center and Phobia Institute in Asheville, North Carolina, estimates that between $800m and $900m is lost in business on Friday the 13th because people do not fly or do business they would normally do.
In the Spanish-speaking world, it is Tuesday the 13th as well as Tuesdays in general that are believed to bring bad luck.
Ozzy Osbourne's former band, Black Sabbath, released their self-titled debut album in the UK on Friday, 13 February 1970.