Plato Timaeus 38

For we say that it is or was or will be, whereas, in truth of speech, is alone 38a is the appropriate term; was and will be, on the other hand, are terms properly applicable to the Becoming which proceeds in Time, since both of these are motions; but it belongs not to that which is ever changeless in its uniformity to become either older or younger through time, nor ever to have become so, nor to be so now, nor to be about to be so hereafter, nor in general to be subject to any of the conditions which Becoming has attached to the things which move in the world of Sense, these being generated forms of Time, which imitates Eternity and circles round according to number. And besides these we make use of the following expressions,— 38b that what is become is become, and what is becoming is becoming, and what is about to become is about to become, and what is non-existent is non-existent; but none of these expressions is accurate. ¹ But the present is not, perhaps, a fitting occasion for an exact discussion of these matters.
  Time, then, came into existence along with the Heaven, to the end that having been generated together they might also be dissolved together, if ever a dissolution of them should take place; and it was made after the pattern of the Eternal Nature, to the end that it might be as like thereto as possible; for whereas the pattern is existent through all eternity, 38c the copy, on the other hand, is through all time, continually having existed, existing, and being about to exist. Wherefore, as a consequence of this reasoning and design on the part of God, with a view to the generation of Time, the sun and moon and five other stars, which bear the appellation of planets, came into existence for the determining and preserving of the numbers of Time. And when God had made the bodies of each of them He placed them in the orbits along which the revolution of the Other was moving, seven orbits for the seven bodies. ² . 38d The Moon He placed in the first circle around the Earth, the Sun in the second above the Earth; and the Morning Star ³ and the Star called Sacred to Hermes He placed in those circles which move in an orbit equal to the Sun in velocity, but endowed with a power ⁴ contrary thereto; whence it is that the Sun and the Star of Hermes and the Morning Star regularly overtake and are overtaken by one another. As to the rest of the stars, were one to describe in detail the positions in which He set them, and all the reasons therefor, 38e the description, though but subsidiary, would prove a heavier task than the main argument which it subserves. Later on, perhaps, at our leisure these points may receive the attention they merit.