... is that it will invalidate all patents as "prior art".

But what you just need in this case is not pure time travel, but only the ability to send information back in time. Which brings the interesting question - assuming that there is a physical way to send information back in time, how this would affect computing?

Sending information forward in time is trivial. All you need is to store the immutable data on some persistent medium like a tape or a harddisk. But sending information backwards in time is a little bit more complicated. Let's ignore the "implementation details" for a second. Given that, how would you design the interface of an API to carry out this job?