Ernst Mach (same Mach) critized Newton’s second law of motion as a trivial definition of time.
Einstein showed that how you experience time, as measured by events, depends on your particular frame of reference. The notion that time is some natural force flowing continually and uniformly for all observers is not supported by facts. What is truly remarkable is that time measured quantum electrodynamically by atomic clocks appears to be identical (to a least one part in 10 to the 9) with graviationally determined time as measured by the orbits of planets.
Time shows up as the independent variable in the equations of quantum mechanics and astronomy. Long baseline astronomical observations agree with atomic clocks to about one part in a billion, limited by our knowledge of all the factors perturbing astronomical orbits. Different astronomical clocks (E.g., eclipses of Jupiters moons and occlusion of stars by Neptune) only agree with one another to about one part in a billion, this is attributed to imperfect knowledge of the solar system’s detailed gravitational field. But within the same percision, astronomical clocks agree with atomic clocks.