A fear of both Fridays and the number 13 appear to have their roots in Christian theology. At some point they have combined to produce the superstition regarding Friday the 13th. Some people believe so strongly in its power that they suffer from paraskevidekatriaphobia, or a deep fear of Friday the 13th.

Friday the 13th can occur a maximum of three times per year. It will occur three times in a year if the first falls in February during a non leap-year. The next will then occur in March and the third in November.

The most common reasons, as discussed by several sources, for the fear and superstition surrounding the day are:

• 13 men were present at the Last Supper
• Christ was crucified on a Friday
• There are 13 witches in a coven
• The Norse God of Evil, Loki, gatecrashed a banquet of 12 gods at Valhalla (bringing the total number of diners to 13)
• Friday was the day for public hangings in Britain and there were apparently 13 steps leading up to the noose

The most interesting theory I read was that it stems from primitive man and his ability to count. According to this theory primitive man, having 10 fingers and two feet, could not count higher than twelve. Thus, there was mystery surrounding what was beyond twelve and from there the fear and superstition arose. (Primitive man must have been pretty good to manage life without toes!)

However, throughout history, Friday the 13th has been considered lucky by some cultures. The ancient Egyptians believed in 13 stages of life. The 13th stage was death or the afterlife. This was celebrated and revered by the Egyptians, so the association with the number 13 was of no concern to them.

The name Friday comes from the Anglo-Saxon "Frigedaeg" or Frigg's Day. In Norse mythology Frigg was the Goddess of Love. The Scandinavians believed Friday was their luckiest day, associated as it was with love and fertility.

To the Chinese, the literal meaning of the number 13 is 'alive' and therefore is considered quite lucky.

Although the theories point to historical events as the reason for Friday the 13th being considered unlucky, it is quite likely that the superstition surrounding the day has a much more modern origin. There is, according to one source, a lack of documented evidence to support the existence of this superstition prior to the 1800s. This has led some scholars to believe that Friday the 13th's reputation has been exacerbated by media hype.

Whatever, the true origin of this superstition, it remains a widespread belief, and is commented upon by all and sundry when it occurs.