I mean, he didn't discover time travel lol. I think Doom did that in Marvel. He's just built time machines, like he did in one of those Stan Lee issues with Marcos Martin for example. Peter has built AIs during his time at Parker Industries. They weren't like Ultron or anything, just your average robots. I also don't see why it's out of character for Peter to build any of those things? He's a scientist, that's what he does...