Time Travel

Time travel is an extremely dangerous magical effect which allows a person to travel back in time. Because of the potential for catastrophe should history be altered, time travel is all but forbidden in wizarding society. Certain magical devices can be used for time travel, but access to them is strictly controlled.

References from the canon

• Hermione once used a Time-Turner to repeat hours of the day and take more classes than would otherwise have been possible (PA21).
• The Pensieve and Tom Riddle's diary allowed a form of time travel, although the person or persons traveling were not actually part of the time they entered. Instead, they became observers, unseen and unheard. This form of time travel is tied to stored memories and the traveller views the past from a vantage point near the person whose memories are used. This form of time travel might be better termed "memory travel." (CS13,CS17,GF30, OP28, HBP10, HBP13, HBP17, HBP23, DH33)
• Time is studied in one of the rooms of the Department of Mysteries; a Death Eater whose head fell into a huge bell jar in that room was changed from the neck up into a baby (OP35).