What Is Time?
Time is the opposite of the speed of light and also a locally constant rate of elapse with respect to a reference frame which is not moving through the universe at light speed.
If everything moved at the speed of light, nothing would happen. At light speed there are no antecedents, no precursors.
Time is a special constant rate set by the universe that is relative to any reference frame. Time is not universally consistent - it is an unequal rate when comparing two reference frames.
The universe is a two-sided coin: on one side is the speed of light (the maximum speed available - the maximum speed of causality itself). Because nothing can happen at the speed of light in a reference frame, light speed could be considered a zero/negative/false state - impossible for any thing to achieve because we live in a world where things happen.
On the other side of that coin is time. Any thing that moves even a little bit slower than the speed of light is where you get events that elapse in reference frames. Things happening in reference frames could be considered a positive/true/1 state.
Strangely, someone moving at slightly less than light speed in a closed box would not notice anything out of the ordinary going on. Their perception of time in their reference frame of the box wouldn’t be much different than our perception of time here on earth in our local reference frame of earth.
When things move any slower than light speed, a locally constant rate of elapse emerges unique to any reference frame. Though time is locally constant within any reference frame, comparing time between two reference frames differs and those differences are caused by unequal gravity and movement forces.