It cannot be possible.
If it was possible we'd already know because time travelers would be amongst us or there would be 800 billion people at the Sermon on the Mount.
Also, it violates pretty much every known law of physics.
Those cavaets out of the way, yeah why not?
This. The only way you can possibly alter time in any noticeable way is through orbiting larger objects.
Going back in time through a machine will always be science fiction.