### Brain Teasers

# Friday the 13th

When's the next year when there won't be a Friday the 13th?

### Answer

Never.The 13th of each month will fall on different days, according to a complex pattern which takes several years to repeat, because of Leap Years. However, each day of the week comes up as the 13th within the first 9 or 10 months every year.

Assign A, B, C, D, E, F, & G randomly to Sun, Mon ... Sat.

If we assume, in a non leap year, that:

* 13 Jan is Day A, then

* 13 Feb is Day D,

* 13 Mar is Day D,

* 13 Apr is Day G,

* 13 May is Day B,

* 13 Jun is Day E,

* 13 Jly is Day G,

* 13 Aug is Day C,

* 13 Sep is Day F

Thus all seven possible days of the week have been used, within a 9-month period.

Similarly, in a leap year:

* 13 Jan is Day A, then

* 13 Feb is Day D,

* 13 Mar is Day E,

* 13 Apr is Day A,

* 13 May is Day C,

* 13 Jun is Day F,

* 13 Jly is Day A,

* 13 Aug is Day D,

* 13 Sep is Day G,

* 13 Oct is Day B,

Thus all seven possible days of the week have been used, within a 10-month period.

Hide Answer Show Answer

## What Next?

**Solve a Similar Brain Teaser...**

Or, get a random brain teaser.

If you become a registered user you can vote on this brain teaser, keep track of

which ones you have seen, and even make your own.

## Follow Braingle!