Isn't this meant to be Impossible?

Hermione once told Harry bad things happen to wizards that mess with time... she said nothing about what happened to wizards that time messes with. Thrown back to 1941 then back to his own time Harry gets to deal with being torn between his Gryffindor friends and the Slytherins from 1941. Because everyone knows Tom's a possessive genius. and Time means nothing to him.