■嘘つき妖怪■ じじいの発音 part4 ■通じません■

Cambridge Advanced Learner's Dictionary
http://dictionary.cambridge.org/define.asp?key=39636&dict=CALD

in (BEFORE THE END)（未満）
preposition
before or at the end of a particular period:
Dinner will be ready in ten minutes.
We'll all be dead in a hundred years so there's no point worrying about it.
I'm just setting off, so I should be with you in half an hour.