The idea that a well-defined now exists throughout the universe is an illusion, an illegitimate extrapolation of our own experience - Carlo Rovelli

What is then the physical content of a solution of Einstein's equations..? ...[C]onsider what is actually measured in general relativistic experiments. ...Consider a clock at rest on ...Earth and a clock on a satellite in orbit around the Earth. ...Call T₁ and T₂ the readings... Each measures the along its own worldline, in the Earth gravitational field. ...the theory predicts the value of T₂ that will be associated to each value of T₁. Or vice versa.

While non-relativistic time is the observable quantity measured (or approximated) by physical clocks, in general relativity clocks measure s along their worldline, not t. The relativistic... t is a freely chosen label with no direct physical interpretation. ...The physical content of a solution of Einstein's equations is not in its dependence on t, but ...in what remains once the dependence on t (and x) has been factored away.

Hawking was one of the good physicists of his generation, not the universal genius the popular press has depicted. It is a pity, because this confusion fogs the memory of a remarkable man.