It might be considered that defining time in relation to movement or velocity is self referential as time is part of the equation i.e velocity is distance over time. Defining time in such a way is circular and logically inconsistent.
Clearly, time is a measurement between two events occurring. A measurement arbitrarily ascribed however we wish to, in ever decreasing increments and in figures so large as to reel the mind. But these labels are relative to what we perceive and what can be measured, such as the speed of my typing, the speed of light (no relation), the positions of things, even subatomic particles (which is quite another sticky mess according to Heisenberg's Uncertainty Principle)
Physics doesn't require time move in one direction only as the math allows events to happen forwards or backwards in time. Such is how the Big Bang theory was postulated, working things backward. In relativistic terms, speed and therefore time are finite in that the speed of light governs all. Then again, quantum entanglement seemingly allows events to affect each other instantly regardless of distance and time. This begs the question of what is an instant?
What really is time?