Mais si, it adds up! Fifteen days hung around fourteen nights - makes perfect sense.When you book into a hotel for Saturday night, you can spend two days there - Saturday and Sunday. This is the same thing over a longer time period.

Mais non, Bridget. If you calculate it that way we should really be saying seize jours, not quinze. Write it out on a piece of paper and you will see that I am right.

Typically, most people work from Monday to Friday. When they go on vacation/holiday they start on the Saturday and finish on the Sunday of the second week, as follows...

Sat, Sun, Mon, Tue, Wed, Th, Fr, Sat, Sun, Mon, Tue, Wed, Th, Fr, Sat, Sun.

A total of seize jours, not quinze.