Depends on Your Perspective

After an enjoyable evening out with colleagues, a mathematician finally got home at 3 am. She quietly opened the door and tip-toed to bed...but her angry husband confronted her with the words: "You're late! You said you'd be home by 11:45."

Without hesitating, the mathematician replied, "I am not late! I am exactly on time, as I said I would be home at a quarter of twelve."