This question already has an answer here:
In Harry Potter and the Prisoner of Azkaban, Hermione mentions:
Awful things happen to wizards who meddle with time.
Now, I can imagine what could go wrong logically, for example, their past self could harm their future self perceiving some danger owing to the confusion and chaos, et cetera, et cetera.
But what I was wondering is, if there is a mention, in the book, of any such incidents that might have happened actually in the past to some other wizards?