It's a question that can't be answered without first acquiring lots of observable data over a wide range of phenomena.
We know that time runs slower here on the earth as opposed to out in space. But that belief is based on atomic decay rates that decay faster out in space. And it may turn out that it is just the way nuclear force behaves in the presence of gravity.
Nevertheless there has to be some starting point or general consensus on which way to proceed in the investigation of what time is. So I chose the wave theory approach. Where TIME is just a force expressing itself as a wave. It would appear to be a standing wave to us. So far I have not come across any phenomena which would suggest otherwise. In fact we have many phenomena to examine that show us how waves work. So based on this starting point knowledge I proceeded to look for any phenomena that deviates from the norm.
So far I have two candidates for further investigation. Tesla's Zero Time Reference Generator and the four configurations to make a Tesla coil.
The Zero Time Reference Generator exhibits a rotation phenomena in its horizontal plane. Right after it transitions a directional change in rotation, the rpm of the device speeds up on its own. That indicates a wave phenomena that just experienced a TIME reversal. Kind of like the direction of weight in an inertial force flipped its direction to align with the acceleration of the device.
In the above video I'm running four Tesla coils that are being turned on and off in a rotating pattern. These are negative voltage coils. Two of them are clockwise winding. The other two are counterclockwise windings. I never did figure out why they make the whistling sound. I have nothing in the electronics that is running at those sound frequencies heard. But the coils react to my hands position in relation to the coils. It's like time speeds up when moving my hand toward the left coil. And time slows down when moving my hand toward the right coil.