Your questions presumes time travel and spacial travel are tightly linked.That is, travel backwards 15 years means returning everything to it's place in the past.I doubt things are linked in that way.Science does not understand the concept of negative time, yet. Although it certainly shows up in the math used to solve physics problems, even in high school. Students are taught to throw that answer away, so, no wonder we do not understand it.I cannot share your desire to return things as they were in 1985 since that year was a bad one for me.Maybe the inertia of changing everything "back to the way it was" or "building what will be" is the reason time travel has eluded us.Hope life gets better for you.