Black holes are places where gravity is so strong that it draws everything, including light and all forms of radiation, back into it. There is no law in physics that doesn't allow physics, but there is nothing that supports it, either. In any event, the only way to travel backwards in time is to travel faster than 180,000 miles per second, which is the speed of light. It is impossible for objects to cross the light barrier, so travel backwards in time that way is impossible. Travel forward into the future can be accomplished by two known and accepted ways: by being in a strong gravitational field, which bends space and time, or by traveling close to the speed of light, which also slows down time. in either case, time, as experienced by the person in the gravitational field or traveling at high speeds, will slow down, but time for everyone else will not.