Sextus Empiricus Pyrrhoniae Hypotyposes 3.19.143

[143] Further, if time exists it is either divisible or indivisible. Now it is not indivisible; for it is divided, as they themselves declare, into present, past, and future. Yet it is not divisible either. For each divisible thing is measured by some part of itself, the measure coinciding with each part of the measured, as when we measure a cubit by a finger. But time cannot be measured by any part of itself. If, for instance, the present measures the past, it will coincide with the past and will therefore be past, and similarly it will be future in the case of the future. And if the future should measure the rest, it will be present and past, and so likewise the past will be future and present; which is nonsense. Neither, then, is time divisible. But if it is neither indivisible nor divisible, it does not exist.