NO ABSOLUTE TIME

One of the first results of Einstein’s speed-of-light axiom is the fact that there can be no such thing as an absolute time standard. It is impossible to synchronize the clocks of two observers so that they will see both clocks as being in exact agreement unless both observers occupy the exact same point in space.
In recent decades we have built atomic clocks, and we claim they are accurate to within billionths of a second (where a billionth is 0.000000001 or 10^-9). But this has meaning only when we are right next to such a clock. If we move a little distance away from the clock, the light (or any other signal that we know of) takes some time to get to us, and this throws the clock reading off.
The speed of EM-field propagation, the fastest speed known, is approximately 3.00 × 10⁸ m/s (1.86 × 10⁵ mi/s). A beam of light therefore travels about 300 m (984 ft) in 1.00 × 10^-6 s (1.00 μs). If you move a little more than the length of a football field away from a superaccurate billionth-of-asecond atomic clock, the clock will appear to be in error by 1.00 μs. If you go to the other side of the world, where the radio signal from that clock must travel 20,000 km (12,500 mi) to reach you, the time reading will be off by 0.067 s. If you go to the Moon, which is about 4.0 × 10⁵ km (2.5 × 10⁵ mi) distant, the clock will be off by approximately 1.3 s.
If scientists ever discover an energy field that can travel through space instantaneously regardless of the distance, then the conundrum of absolute time will be resolved. In practical scenarios, however, the speed of light is the fastest possible speed. (Some recent experiments suggest that certain effects can propagate faster than the speed of light over short distances, but no one has demonstrated this on a large scale yet, much less used such effects to transmit any information such as data from an atomic clock.) We can say that the speed of light is the speed of time. Distance and time are inextricably related.