Here is the Friday puzzle!  Solution on Monday.

The day before yesterday Joan was 17.  Next year she will be 20.  How can that be the case?

I have produced an ebook containing 101 of the previous Friday Puzzles! It is called PUZZLED and is available for the Kindle (UK here and USA here) and on the iBookstore (UK here in the USA here). You can try 101 of the puzzles for free here.