Yesterday was Friday 13th. According to Wikipedia, the traditional belief that Friday 13th is unlucky started exactly 699 years ago:
There have been a number of events known as “Black Fridays“ in history. Usually, these events are devastating. Some historians propose that the origin of the “Black Friday” was the simultaneous arrest of hundreds of Knights Templars on October 13, 1307 (Friday), to be later tortured into admitting heresy.
It is interesting to note that 2006-13-10 adds up to 13 (2+6+1+3+1). It also adds up to 2029 (2006+13+10) that in turn adds up to 13 (2+2+9), again.
Now, since I’m a geek, I have also to note that the Gregorian calendar makes the 13th of each month slightly most likely to be on a Friday. Since not all months have the same length, it happens that on the 13th of the 4800 months composing a 400-years cycle we have 688 Fridays, 687 Sundays and Wednesdays, 685 Mondays and Tuesdays, 684 Thursdays and Saturdays. Wow, Friday 13th is 0.048% more likely than average 13th…. I mean, there has to be something fishy going on.