Metaphysics - time?

A simple way to travel back in time. Let's assume that you have isolated a mouse in a cage. The walls of the cage are all blank. A piece of cheese is placed in front of it everyday for one week. Then afterwards for the next week the piece of cheese is not placed  in front of it. You change nothing else.

After one week, you place the cheese is placed back in front of the mouse. To the mouse it has traveled back in time. This is because it cannot perceive time and the return of circumstances to the way they were is time travel.

I'm trying to say that time is something we created to explain changes to the physical world. Unlike distance, light or other forces, time has no physical basis. There are no quarks or waves or particles to explain it. It is our own creation.

I saw a movie recently staring George Clooney that explored time dilation. In the movie a space ship travels to a planet that is very near to a black hole.While the ship stays at a distance away from the black hole's gravitational pull, Clooney and a few others use a space ship to travel to the planet. Then here's where it gets dicey. The crew stay on the planet for a few hours but when they manage to get back to the ship, thirty years have passed!

Let us hypothetically assume that it is possible to create a clock that is unaffected by gravitational waves. If both the crew and those who left for the planet had started this stop watch together at zero before they left for the planet. And then agreed that the crew would stay in the planet for exactly one hour and come back. Would it mean that their stop watch would dramatically slow down when they reached the planet?

We created time. And decided that 12 hours was how long it took to for the sun to move from the east to the west. It is a very useful tool. But it is not based on natural laws.