There is a theory that time is curved. So ultimately if the curve is constant, then sooner or later it will become a perfect circle.
I think it was Einstein who first expostulated this theory, at least in modern western scientific terms. This has been the basis of Hindu and Buddhist beliefs for much longer of course and is evidenced in the representations of Shiva and in Buddhist mandalas.



Shiva dances within the wheel of birth, life,death and rebirth, or if you like, time. As a God, Shiva is able to touch the wheel at any of it's points and even multiple points at once but is still within the wheel. Perhaps that is why Shiva is represented as having many arms?



Traditional Buddhist mandalas pretty much always represent the same circle of time with the deities within it's boundaries and the Buddha at the centre but there are many different mandalas for many different purposes, so this may not always be exactly right.

So what are these representations trying to tell us about time and our place in it? I think it is not only that time is circular or cyclic, but also that it is possible for a God or enlightened one to see the circle in it's entirety and comprehend it as such.

What does this have to do with time travel? I am not sure but if there was some way to cut across the circle instead of trying to speed up or reverse the process, wouldn't that be a more efficient way to travel through time?