Choose a non-Earth-centric time standard. People speculate how a space-faring society would be able to synchronize time and location under relativistic physics.

Choose a non-Earth-centric time standard. People speculate how a space-faring society would be able to synchronize time and location under relativistic physics. The answer is an intergalactic GPS using far away qusar locations and frequencies. The Voyager probes located Earth for a futrue viewer using a quasar GPS.