In "Harry Potter and the Prisoner of Azkaban," Harry's godfather Sirius Black is about to suffer a fate worse than death for a crime he didn't commit, and Buckbeak, Hagrid's beloved hippogriff, has seemingly been executed.

Dumbledore tells Harry and Hermione that by using a Time Turner to go back a couple of hours, "more than one innocent life may be spared tonight."

For a long time, we thought there was no way to turn back the clock on sleep deprivation, not even by packing in extra hours on following nights.

And we know that people who get less than six hours of sleep nightly are more likely to have risk factors for diabetes, heart disease, and stroke.

But evidence is now showing your missed hours of sleep may not be irrevocably damaging after all.

For a new study, researchers looked at data on almost 40,000 people for 13 years and found that there was no difference in death rates between people who had less than six to seven hours of sleep nightly during the week, but slept more on the weekends, and those who consistently had more than seven hours a night.

So it turns out that you catch up on sleep.

Of course, the ideal way is to keep your body clock on the same healthy schedule seven nights a week.

But if during the week, kids, exercise, work, and play don't allow for enough sleep, take extra time to snooze on the weekends. It will help your body repair.