The word philosophy, as distinguished from science, is misleading, for it implies that what philosophy contains is impossible to be a systematic body of knowledge and what science contains is certain or proved.
If the universe is a non-spatial computer, a ‘time machine' is a program that allows a user to have the same (ontologically non-spatial) feelings or experiences that occurred or s/he merely feels to have occurred in the past, with an in-built function to have different feelings or experiences than those of the past, and thus creating a possibility to change the past or to rewrite history in a pseudo sense.
One of the great intellectual mistakes Einstein made is that he thought that space and time are physically or ontologically entangled. In the present non-spatial universal computational program, space and time happen to be entangled to the extent that, under certain unique circumstances, changes in spatial measurements indicate changes in temporal ones. However, a change in the program itself may cause space and time to disentangle.