TIME IS NOT A REALITY OR IS IT? The unit of TIME we use is only constructed by humans for their own convenience based on the movement of stars and planets.
*The below explanations could only be one of the many possible theories out there as suggested by various scholars working on space-time puzzle.
SO, WHAT IS REAL? the reality is made up of GRAVITY, SPACE, MOTION & SIZE.
GRAVITY can slow down motion which could also be interpreted as slowing down time. Time experienced by humans on this planet is different from time experienced by someone in SPACE closer to a black hole with enormous gravity.
Motion of a particle if accelerated to speed of light will slow down time for that particle. In other words that particle moves from a dimension of faster time to a dimension where time moves slow.
If we assume another object that is super-massive and exists in a plane where the unit of measurement is light-years instead of meters, then a normal motion of few units for that object would be equivalent to much faster time lapse for the smaller particle. The particle would have to move at speed of light years to catch up with the super-massive object, in other words to cross dimensions and exist in a dimension where time moves slow.
So time lapse as experienced by a particle or an object, is dependent on its SIZE or its MOTION.
Which brings us back to the question IS TIME REAL? As mentioned above, a combination of GRAVITY, SPACE, MOTION & SIZE is interpreted as TIME, as we know it.
Science fiction often mentions Time-Travel, which in theory is possible but only to future, if MOTION can somehow be controlled to speeds of light-years or maybe even faster than that. Time-Travel to past, is simply not possible as TIME IS NOT REAL, and motion of particles or objects in their respective dimensions of existence is often what gets considered as TIME. Another Science Fiction term known as Grand-Father Paradox, is also unreal and will never happen as Ageing is always a forward motion process.