My point of view about time
The human observer invented the concept of time and clock because it was difficult for him to measure change and speed of change (rapidity of change or slowness of change) which along with: space, matter, energy, forces, fields, .... are fundamental constituents and properties of the universe.
Time is nothing but the relationship between change and the speed of change. Time only makes sense for what is changing at a certain speed, so it is a function of these two.
Time is relative depending on the nature of the change: life time, half-life for radioactive substances, reaction time, astronomical time ....