Plotinos: Complete Works, v. 3 In Chronological Order,...

To begin with, we may divide the generally accepted opinions about time into three classes: time as movement, as something movable, or as some part of movement. It would be too contrary to the notion of time to try to define it as rest, as being at rest, or as some part of rest; for time is incompatible with identity (and consequently with rest, and with what is at rest). Those who consider time as movement, claim that it is either any kind of movement, or the movement of the universe. Those who consider it as something movable are thinking of the sphere of the universe; while those who consider time as some part of movement consider it either as the interval of movement, or as its measure, or as some consequence of movement in general, or regular movement.