Time-Turners

A Time-Turner is used to travel through time. In Harry Potter and the Prisioner of Azkaban, Hermione is given a time-turner by Professor McGonagall so she could attend more than one class at the same time. Hermione is ordered to keep it as a secret from everyone, including Harry and Ron, although they do notice the impossibility of her schedule, and several bizarre disappearances and reappearances. Hermione tells Harry and Ron the secret near the end of the book, where she and Harry use the Time-Turner to save Sirius and Buckbeak. Hermione's Time-Turner resembles an hourglass pendant on a necklace. The number of turns on the hourglass represents the number of hours the user will go back in time. The travel ends when the traveller arrives to the point in time of which she/he went back in time.