[mikewarot]

In physics, perfect clocks, can only perfectly synchronized for a moment of time, from an arbitrary observation point. They will always drift apart, because no two points in the universe have the exact same stress energy tensor across time.

Clocks have improved to the point where a 2 centimeter difference in height in the same room results in an observable difference in time. If you take into effect the gravity of the Sun and Moon, no two points on earth experience the same amount of gravity over time.

Now, if you have a logical clock, you might be able to pull consistency out of this, but the real world doesn't work that way, unless you lower the observation quanta to hours, minutes, seconds, on Earth only, and use UTC which isn't consistent across time.