Hermoines' Time-Turner

The Time Turner represents a tool with which you can travel in time, going backward a few hours. Hermoine got one from McGranitt professor in the third book to allow her to take more than ten study courses due to overlapping of lesson hours.

All around the rings is written the English phrase:" I mark the hours, everyone. Nor have I yet outrun the sun. My use and value unto you, are ganged by what you have to do." [i.e. I can't take you in the future].

The Hermoine's Time-Turner is shaped like a necklace with a small hourglass as a pendant. To travel back in time you need to wear the necklace and turn the hourglass as many times as the number of hours in which you want to go back. The book also mentions other Time-Turner that would allow you to go even further back or even advance in time, arriving in the future. In Harry Potter and the Half-Blood Prince, we learn that they were all destroyed during Hermoine, Harry, Ron, Ginny, Neville and Lune incursion on the Ministry's Department of Mysteries.