It’s Friday The 13th – The One And Only
I hope you're not superstitious, because today is Friday the 13th! So, maybe you better knock on wood, and certainly avoid walking under ladders, breaking mirrors or letting black cats cross your path.
Friday the 13th occurs when the thirteenth day of a month falls on a Friday, which superstition holds to be a day of bad luck. In the Gregorian calendar, this day occurs at least once, but at most three times a year. Any month's 13th day will fall on a Friday if the month starts on a Sunday. Information courtesy of Wikipedia. Just click on Friday the 13th.
There is only one Friday the 13th this year. Last year, we also had one which took place in August, and next year, we have three - January, April and July.