If man's time exist.

Actually, time is somewhat variable. In accordance with General Relativity, time is fastest in flat space, away from massive bodies, and slowest as velocity approaches "c" or in the presence of a truly massive gravitational field, such as a singularity, a black hole, or nearly infinite acceleration. In fact, time is described in terms of "c", and therefore all things do have a "built-in" clock of sorts.

However, the really strange thing about time is that time's passage is constant is constant for all observers in all frames of reference, because the speed of light is also constant. Which can mean that if we were to boost out from Earth at one gravity and travel to Alpha Centauri, upon arrival we would perceive that about 24 months had passed, while back home it will have been something more like six years. General Relativity can be pretty hard to wrap your mind around, but it's worth the effort to study it.

DrMoose