Back to the Future plot hole: Doc’s calculations WRONG – Marty returned to 1985 by chance

However, they would have had no idea when during those sixty seconds this happened.

And since only Doc and Marty were present on the street at that time on November 12, no one would have seen it, even in the original timeline when they weren’t there.

But adding to this problem of guessing when lightning would strike within that minute, the fan theorist points out how Marty missed Doc’s calculated start time to reach 88mph and pass the Clock Tower at the exact moment lightning struck – which, as said, the scientist didn’t know anyway.

So if anything, it’s complete chance that Marty managed to pass at just the right time and be sent back to the future given his delayed start and lightning striking the Clock Tower when it did.