First, you need a lot of money to buy a large cylinder. When I say large, I mean very large, perhaps a 100km long. The cylinder also needs to be at least the mass of the sun, but very densely packed together. You then need to start it rotating, faster and faster, until it's rotating so fast that it starts to disturb the fabric of both space and time – and you would be able to detect a wash of gravity waves coming from this structure.
I also need to add a health warning, as coming close to such a dense structure would cause issues. The mass of the Earth pulls us down to its surface, but getting too close to an object this massive would be hugely dangerous – it would drag you towards it and squash you flat.
If you can get round this squashing problem, however, approach the rotating cylinder and start following its spin – as you get closer, strange things will start to happen. Your path, which normally inextricably moves you forward in time, changes, since moving around the cylinder in the direction of rotation will shift you back in time. The machine makes the direction of time
collapse into the past, so the longer you follow the machine's spin, the further back in time you will go. To reset the movement to normal, simply move away from the cylinder, go back to Earth and you will be returned to the present – albeit a present in the past.
