Time is the continuous sequence of existence and events that occur in apparently irreversible succession from the past through the present to the future.(wiki)
We perceive time through events we see. Hence as soon as the "light" from those events reaches our eyes, we see them happening and changing. Where there is light, there is time. And we know that gravity distorts time. More the gravity, time slows down and less gravity, time speeds up. This is why inside a black hole , it is assumed that there is no time since the gravity is immense. Thus the union of time and gravity gives rise to the dimension of time( according to me). Time is something we're confined under. We cannot imagine a world beyond time. We are incapable of perceiving the VOID.
interesting thought:
Of these three divisions of time [past, present, and future], then how can two, the past and the future, be, when the past no longer is and the future is not yet? As for the present, if it were always present and never moved on to become the past, it would not be time but eternity. If, therefore, the present time is time only by reason of the fact that it moves on to become the past, how can we say that even the present is, when the reason why it is that it is not to be? In other words, we cannot rightly say that time is, except by reason of its impending state of not being. – St. Augustine; The Confessions, Book XI