Missed my window to catch the school bus for a field trip for our choir. It was Sunday evening and my parents were freaking out with me trying to get me ready (since they had assumed our time to leave was 6:30 PM not that I thought it was already Monday morning). It was embarrassing as all get out when I pulled up to the school to see it locked and empty. They laughed their heads off.
It was because I took such a long Sunday nap that I thought it was morning.