Time has two aspects

Time goes in cycles, as well as in a line. A planet revolving: you see? One cycle, one orbit around the sun, is a year, isn't it? And two orbits, two years; and so on, one can count the orbits endlessly – an observer can. Indeed such a system is how we count time – it constitutes the time-teller, the clock. But within the system, the cycle, where is time? Where is beginning or end? Infinite repetition is an atemporal process. It must be compared, referred to some other cyclic or non-cyclic process, to be seen as temporal. Well, this is very queer and interesting, you see. The atoms, you know, have a cyclic motion. The stable compounds are made of constituents that have a regular, periodic motion relative to one another. In fact, it is the tony time-reversible cycles of the atom that give matter enough permanence that evolution is possible. The little timelessnesses added together make up time. And then on the big scale, the cosmos: well, you know we think that the whole universe is a cyclic process, an oscillation of expansion and contraction, without any before or after. Only within each of the great cycles, where we live, only there is there linear time, evolution, change. So then time has two aspects. There is the arrow, the running river, without which there is no change, no progress, or direction, or creation. And there is the circle or the cycle, without which there is chaos, meaningless succession of instants, a world without clocks or seasons or promises.
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Can one dismiss either being, or becoming, as an illusion? Becoming without being is meaningless. Being without becoming is a big bore... If the mind is able to perceive time in both these ways, then a true chonosophy should provide a field in which relation of the two aspects or processes of time could be understood.

Ursula Le Guin, The Dispossessed (Gollancz, 2002) pp. 185-186