A while ago, a friend was talking about running an Underdark-style campaign in a world of his own creation, and was stuck on how people would tell time and handle scheduling/logistics without the sun. The official Underdark uses various forms of magic for this purpose, and it was clear that he wanted something similar that made sense in his campaign. But I reached a different conclusion:

What if societies living underground didn’t actually keep careful track of time?

In the real world, humans deprived of time indicators will usually settle on a circadian rhythm of a little more than a day, but the exact amount varies from person to person. Fantasy races, particularly the long-lived elves and dwarves so common in stocking local underworlds, might have an even longer one. Deprived of an external conception of a day, does a dwarf sleep the same number of times as a human in a given lifespan, the dwarf’s days just longer?

From day to day, in pre-industrial societies, loose timekeeping by the sun has a lot to do with just making maximum use of the sunlight. You don’t want to be caught hunting far from the village when it gets dark, or fail to get vital chores done around the farm that you can’t do in the dark and which won’t keep until tomorrow. But if your fantasy underworld already supposes some form of chemical or magical artificial light, the actual time of “day” doesn’t make much difference to your ability to function.

Longer-form timekeeping is mostly for tracking the seasons, primarily for food production and preparing for winter. But, again, presumably whatever climate and food sources prevail underground don’t really vary that much over the course of a “year.” You only really care how long things take if you’re reliant on shipments from outside your locale, and I argue that you can just as easily judge those by consumption as on time (e.g., “We usually put in a new order for grain from the surfacers when the silos are about half empty, and it winds up showing up in time.”). Rules of thumb based on travel can also emerge (“The regional peddler usually has done three circuits through his territory by the time the grain shipment comes in, and he’s done four so it’s well late.”).

At the very least, a campaign predicated on fuzzy timekeeping would be an interesting head trip. GMs would have to revise their descriptive language. Instead of, “it takes you until noon to get to the ruins,” you say, “it takes you a little while to get there, and you’re starting to get hungry.” You have to track sleeps instead of days and distances traveled instead of hours. I suspect the feel of the campaign could become rather dreamlike, particularly in long journeys through the dark that take as long as they take.

It could also result in some interesting fodder for worldbuilding:

  • Chaotic societies are always awake. Each individual sleeps when his or her own circadian rhythm calls for it, resulting in a haphazard rotating schedule. Canny adventurers can wait for an opportunity when most of the guards happen to sync up their sleep and the fortress is understaffed.
  • Lawful societies are regimented by the ruler’s preferred rhythms, employing loud bells and civil employees to wake the populace with their leaders, and trying to regiment the day as best as possible. Without access to a true mechanical clock, however, it’s all guesswork leading to a layer of frustration and sleep deprivation among many.
  • Crafters, particularly high-end ones, will complete your item at some arbitrary point in the future but can’t give you any specifics. Dwarves are especially likely to zone out on a job: the item you ordered is twice as good as you expected, but showed up excessively long after you needed it.
  • Time varies drastically from region to region, even in lawful societies, as it’s hard to maintain any kind of regularity across distance. Passage from place to place is a strange dream where it’s never the time you expected when you return.

Ultimately, I think it would be an interesting experiment in making the Underdark feel truly alien to the surface world. You go beneath the world and lose time upon your return… not from any faerie magic, but just because of your own untrustworthy internal clock.