The Rewindable Clock

The unthinkable happens. Keisha forgets to do her science homework! The morning it's due, she rushes to Locker 37 and the locker gives her a clock. Not just any clock, mind you. It's a time-travel device that sends Keisha back to whatever time of day she wants during that particular school day, which means she can scrape together enough time in between her classes to finish her homework