All I'm going to say at the moment is; What he meant was "processes" will slow down/speed up under the influence of gravity and velocity.
Time it-self is not relative. Time is absolutely absolute and completely immeasurable. If it is One'o'clock in Kansas it is One'o'clock inside V4641 Sgr, One'o'clock in the "empty" space outside our universe.
More on that subject on a later time.