Today is Friday the 13th, considered by some to be a very unlucky day, and for those with paraskavedekatriaphobia (fear of Friday the 13th) or triskaidekaphobia (fear of the number 13) it is especially troubling. In the USA, it is estimated that around 21 million people (8% of the population) have a significant fear of this date.

There are a number of theories as to why this particular date has been considered unlucky, though the true origins have been long lost. Some of the more popular theories plant the roots in a mixture of Christian and Norse tradition.