After reading Harry Potter and the Cursed Child, many fans were left upset and with plenty of questions. Namely: why ruin the magic of Harry Potter with the insufferable Albus Potter? However, a closer look at J.K. Rowling's ebooks of Hogwarts prove that everything Albus did in Cursed Child shouldn't have happened.
For those of us who read through the play fast and forgot what happened: Albus uses a Time Turner to go back in time and stop Cedric Diggory from dying. The Time Turner is used again to go to the day Harry's parents died and to stop Voldemort's daughter evil plan (commence my eye-rolling).
However, according to Cosmopolitan, Rowling wrote in Hogwarts: An Incomplete and Unreliable Guide the following: "All attempts to travel back further than a few hours have resulted in catastrophic harm to the witch or wizard involved. It was not realized for many years why time travelers over great distances never survived their journeys." Essentially, Albus and everyone else involved in traveling back in time twice (!) should've had "catastrophic harm" done to them.
But considering this isn't Hogwarts: A History nor a book on a list of school supplies needed at Hogwarts, we might not want to take it so seriously. After all, it does say "incomplete and unreliable guide."