"If anyone shows me negative time, I will ask why they can't see anti-gravity. Unless you can show it."

I believe you are seeing anti-gravity in the flight characteristics of certain UFOs as well as canceling the property of inertia inside the craft. ?????????
The Inflation theory, which I don't believe in, uses anti-gravity to explain itself. Also, some theories about dark energy uses the concept of anti-gravity over galactic distances.

Negative quantum time exists - not going back in time in our mega universe. However, the possibility does exist but it is so rare as to never happen.
Richard Feynman explains how an electron can go back in time, but I wouldn't want to give you a headache.