Are there different measures of time?

Answer 1

Yes, there are as many arbitrary measures of time, as there are measuring instruments for it.

We may have an instrument whose measurement system is extremely regular, but it could still be running fast or slow, compared with another standard, such as sidereal time, or some other astronomical time.

For convenience, the Bureau of Weights and Measures (BIPM) has by international agreement set up UTC (or UTC1).

[Coordinated Universal Time (CUT) in English, and TUC (Temps Universel Coordinne) in French; and the best compromise was UTC!].

This is currently determined by using Atomic locks, which have most excellent stability.

However, if you were on say, Io, one of the moons of Jupiter, then time would pass differently, due to relativistic effects of local gravity and velocities caused by the accelerations.

These corrections do have to be allowed for on atomic clocks flying in the various satellites. Fortunately, by chance, these two effects tend to cancel each other out.