To wrap up this discussion of time, let’s leap back from the micro level of seconds and minutes and hours to the extremely macro level — which is to say, how we think of time progressing in general.
In the West nowadays we tend toward a mode of thinking we inherited from the Enlightenment and the Victorians, which is a narrative of Time as Progress. Although we go through periods of pessimism and dystopian prediction (especially as seen in the commercial genre of science fiction), we still think of the arc of history as bending toward justice, improvement, and a general upward trend.
This is especially true in technological terms, where (barring outright collapse) we assume our tools will steadily become more effective and advanced. But it’s also true in social terms; we trumpet our superiority over the benighted past, and easily forget that rights which have been gained can be lost, groups that have been accepted can be cast out again.
But as that parenthetical in the last paragraph notes, the general upward trend isn’t guaranteed even on the technological level. The Antikythera mechanism is an astonishing achievement of gearing and mathematics from the first or second century B.C.; nothing like it was made again until about fifteen hundred years later. The Minoans and Harappans had a form of flush toilets in the second millennium B.C., while three thousand years later my European ancestors were crapping in pots and throwing the results out the window. It doesn’t even take full societal collapse to turn that progress upside-down.
Which wouldn’t have come as news to many of our ancestors. The second concept of time is the inverse of the first: Time as Decline. We have that in the West, too, in the form of the Fall, the expulsion from Eden, the lost golden age. For many cultures, history is the long litany of how things have not improved, but degenerated.
You see this in the Hindu concept of the four yugas or ages, starting with the idyllic Satya Yuga, then the less ideal Treta Yuga, then the even less ideal Dvapara Yuga (when the great Hindu epics take place), then the final, fallen Kali Yuga — the age we live in now. The Greco-Roman Ages of Man are essentially the same idea, though Hesiod’s version introduces a fifth, Heroic Age in between the Bronze and Iron Ages, perhaps echoing the setting of the Ramayana and Mahabharata in the later Dvapara Yuga.
Interestingly, Hesiod’s account of the Ages of Man echoes another culture — one that, unlike India, could not possibly have had any contact with ancient Greece. Hesiod doesn’t merely have humans declining in quality throughout the ages; he says there have been entirely different iterations of our species, with the previous ones going away to become spirits or residents of the underworld. And if you cross the Atlantic ocean, you find that same idea in Mesoamerica.
According to the Mayan Popol Vuh, gods tried repeatedly to create human beings. But their early attempts didn’t produce the idyllic first ages seen in Greek and Hindu myth; instead their creations were imperfect — incapable of counting time and honoring the gods as desired — and the gods kept destroying them in order to try again. (In some versions, the descendants of one of those previous attempts live on in our world as monkeys.) The Aztecs had a similar story, and spoke of those earlier periods as a series of Suns, with our world being the Fifth Sun.
This brings us to the third concept of time: Time as Cycle. The previous two concepts could be graphed as upward or downward lines, maybe with variations along the way, but generally trending in one direction or the other; cyclical time, by contrast, goes in a circle. What goes down will eventually come up again, and vice versa. Everything will eventually return to where it began.
It would be a mistake to lean too hard on the distinctions between these ways of thinking. The Victorians were perfectly capable of embracing both the narrative of the Fall (time as decline) and an overwhelming narrative of improvement (time as progress). The cyclical Suns of Aztec cosmology included improvement, with the gods iterating their creation until they got the result they wanted. People can and do hold more than one image of time in their minds simultaneously.
But it’s still useful to consider how your invented society thinks about time, because it says a lot about how they feel they fit into the world around them, and why that world is in its current state. Time as Decline is a way of explaining crime and other social breakdowns: once everything was great, but we’re the dregs of that glory, the Iron Age, the Kali Yuga, the Age of Dharma Decline. Time as Progress, on the other hand, positions current humanity as an improvement over the past, and both urges people to become better . . . and justifies what they’re doing now. Time as Cycle is about patterns, seeing parallels to existing conditions in past situations, and remembering that what goes up will inevitably go down (and vice versa).
Characters steeped in these various modes will act differently. If you generally believe the past was more virtuous, you’re more likely to honor your ancestors and look to them for guidance, to justify your actions on the basis of past example, and to see tradition as a precious thing. If you believe the past was benighted, you’re not necessarily going to spit on your ancestors — but tradition is more likely to be seen as dead weight, and you’re more likely to justify your actions on the basis of future goals. If you see it as a cycle, you might become fatalistic, believing that nothing you do will affect the cycle — or you might try to leverage your understanding of that cycle to make the best use of your current position.
Not every book is going to grapple with these issues on a cosmological level, or even on the level of hundreds or thousands of years of history. (We’re not all writing the Foundation series, or a James Michener novel.) But they still color the way the tale is told, and if you don’t think about them consciously, your own built-in concept of time is likely to be the one that takes hold.