Yes in a way a black hole can act as a time machine. Now, a black hole is just a star like our sun. Our sun is an average star. In a way that our sun works is fact that is ball of hydrogen gas and the gravity of gas is colliding the hydrogen atoms together. As the hydrogen atoms collide together they form helium atoms and there is a little difference between the mass of helium and hydrogen atoms. That little difference in mass results in light and heat in the form of energy. But eventually what will happen is that this internal furnace will begin to get used up and when that happens the gravity of the star that pushes the star inward will not going to be balanced by the internal energy that’s pushing it outward and the star is going to collapse.