To change the past, there is no need to travel in a time machine. You can change the past by remote control.
Here's how it works: From beyond the continuum of time, G‑d looks at your stance in this moment now. From that point, He creates all things—of now, of the future and of the past.
With each new moment of now, all of past, as well, is regenerated as though it never was. Change the present now, and you will have changed the past along with it.