If in the future humans master time travel, might it be valuable to know a Universal Reference point that is common to both the present and past coordinates in space and time. For example, say we designated a single point on Earth from which all other relativistic effects are to be measured against. We could set this point as a microdot in a NIST building, sitting on a pedestal and when we created it we'd stamp the exact time, position to the sun and moon and all sorts of other data beside it. Everyone in the world who thought time travel may be possible in their life times invests in an atomic watch with GPS and the watch always calculates your relative position in time and space versus the NIST dot and it takes into the relativistic effects of you moving about in your life 1000s of miles away from the dot. The watch also downloads and tracks the movements of the Earth in the solar system, the solar system in the galaxy, and the galaxy in the cluster? with the goal of making the dot an inertial reference point in time. Who knows what form of time travel if any will be available in the future, this universal reference point may be useful or never, I am not sure.