Paraskevidekatriaphobia or Friggatriskaidekaphobia, and why I have neither.

It's Friday the 13th.

I used to tell people I was born on Friday the 13th of June.
It wasn't specifically a lie.
It was the kind of thing where originally I didn't know what day I was born and so, to seem interesting, I told people I was born on Friday the 13th, and having told it enough times I started to believe it because I had just kinda forgotten that I didn't actually know in the first place.

But it's not true, sadly. I was born on a Monday.

The whole Friday the 13th superstition has been around for a long time; the first written example is from the mid 19th century, but it's has almost certainly been around as folklore for much, much longer.

As for the basis of the superstition, well, there are all sorts of theories, but I'll do my best.

13 is considered pretty unlucky anyway, especially in England and America. There are plenty of documented cases of building being built without a 13th floor.
One reason could be that 12 is a fairly common number for us: 12 months, 12 Apostles of Jesus, 12 signs of the Zodiac, 12 hours on a clock, 12 Gods of Olympus, etc.
As such we could asscociate 13 with abnormality, which is a common cause of fears.

Friday was supposedly the day that Jesus was crucified, as well as being considered unlucky in The Canterbury Tales.

Now, with all the stigma attached to Friday the 13th, it is inevitable that people will develop a fear towards it. Different sources quote different names, but it is definitely either: paraskevidekatriaphobia, or friggatriskaidekaphobia.
Dr. Donald Dossey suggests that as many as 21 million Americans suffer from this fear. That's 6.8% of Americans.
But then, they are American.
I haven't found any accurate data about the British.

It's a classic irrational fear. It's an old wives tale. There is no scientific evidence for bad luck on Friday the 13th.

You slightly less likely to have a car accident on Friday the 13th. Although it's possible that's because the drivers that are afraid of bad luck on this day just don't drive around if they can avoid it.

If you do ever find any evidence, feel free to disregard it, because almost certainly it will have come as a result of people being nervous about worst case scenarios, and the fear has made them do something stupid. Also, Richard Wiseman from University of Hertfordshire found that people who consider themselves unlucky are more likely to believe in superstitions associated with bad luck.

A good example of this cautiousness surrounding Friday the 13th can be found in the business world, where the National Geographic estimates almost a billion dollars are lost because people will not take the kinds of risks they normally do.

Enjoy your Friday the 13th!