Five Minutes To Midnight?

A cop drives up to lovers lane and spots a car sitting in the dark. He slowly walks up to the car. With his flashlight he spots a girl in the back seat knitting and a boy in the front seat reading a book.

The cop asks the boy how old he is and what he's doing...

The boy answers, "I'm reading a book and I'm 20."

Then the cop asks the girl her age...

The boy quickly replies, "She's knitting and she'll be 18 in about five minutes."