Underground timekeeping

[Razanir]

How would a race keep track of time if they live underground? I'm thinking a civilization that even if they do go above ground, it's not often or significant enough to need to bother keeping track of the seasons, so they have no solar or lunar cycles to care about.

[LibraryOgre]

There are a few magical options suggested in different sources, but for mostly non-magical?

Growth cycle for food crops (likely mushrooms or thermophillic algaes and lichens) or animals ("When the Rothe are in season again, we'll attack!").

[Aliquid]

How would a race keep track of time if they live underground? I'm thinking a civilization that even if they do go above ground, it's not often or significant enough to need to bother keeping track of the seasons, so they have no solar or lunar cycles to care about.

Maybe they don't.

Is keeping track of time really that important? Does it really matter?

I knew someone who grew up in a small village in the middle of nowhere, in a 3rd world country. His family managed to immigrate, and when they were asked their ages... none of them knew. They had to guess, because they didn't bother to keep track of such things in his old culture. He could read and write and had a basic education, but he had no conecpt of keeping track of time beyond what season it was or "morning vs afternoon, vs evening".

[Wraith]

Biological rhythms.

Periods of up to, say, 15 minutes might be counted in heartbeats; assuming you're human and at rest, 10 minutes is vaguely equivalent to 700 beats.

Periods of a day are roughly equivalent to a sleep/wake cycle. Again, using humans as the example, scientific experimentation has shown that when deprived of natural cues such as dawn/dusk and artificial time keeping, we naturally fall into a 24-hour 'day' due to something called the circadian rhythm. It takes about 30 days of deprivation for a contemporary human to reach this equilibrium, but a race that only knows darkness would probably be attuned to it naturally.

The menstrual cycle would account for a period of time roughly equivalent to a month. All humans are slightly different, but 28-30 days is common enough to use as an approximation.

Longer periods.... I guess you would use something like an approximate period of time between a crop being sown and then harvested. Maize takes between 2 and 3 months to grown to maturity, so an underground society might mark a 'season' as being one full crop rotation rather than the 3 equal months and appropriate equinoxes that we use.

Anything longer than that would probably be unnecessary. If there's no concept of the changing of the seasons, the concept of a year would be entirely artificial and probably unnecessary.

[Razanir]

I'm currently thinking of having a decimal system, independent of solar and lunar cycles.

100 seconds = 1 minute
100 minutes = 1 hour
10 hours = 1 day (20 of our hours)
10 days = 1 week
10 weeks = 1 month
10 months = 1 year
10 years = 1 decade
10 decades = 1 century
10 centuries = 1 millennium

And it's for dwarves, so the rigidity of the system makes sense.

[LibraryOgre]

I'm currently thinking of having a decimal system, independent of solar and lunar cycles.

100 seconds = 1 minute
100 minutes = 1 hour
10 hours = 1 day (20 of our hours)
10 days = 1 week
10 weeks = 1 month
10 months = 1 year
10 years = 1 decade
10 decades = 1 century
10 centuries = 1 millennium

And it's for dwarves, so the rigidity of the system makes sense.

Just to add a bit of oddity, why base 10? Why not base 20 (fingers and toes), or base 7 (principle deities of the pantheon, or virtues of dwarvendom, or whatever)?

[Razanir]

Just to add a bit of oddity, why base 10? Why not base 20 (fingers and toes), or base 7 (principle deities of the pantheon, or virtues of dwarvendom, or whatever)?

Same reason the currency system in D&D is decimal. Convenience for players (and DM). But if I really wanted to make it an alien base, it'd be 30 (or 60). You get more prime factors than with base 10.

[TheThan]

How about a clock?

Seriously this isn’t that hard. A clock, even one wound arbitrarily will accurately keep time until it winds down. It’s not too hard to imagine a clock tower in the center of a dwarven hold or some such that is wound at the same time daily. make the people in charge of winding the clock up some sort of special order of monks or something.

[Milodiah]

One thing I found interesting in the book Metro 2033 (not the game) is one of the many philosophical tangents the characters go off on concerns this...the main character comes from a station where the clock is maintained, checked, and nearly revered. However, they come to a broken-down station full of refugees, and he asks how people know what time it is without a working clock. His guide replies that everyone carries his or her own time, much like the smouldering coals of old fires in humanity's earliest days. What may be your morning is his evening. Some people have even lost their coal...

Also, for some underground cultures (such as dwarves) who are even more orderly than humans, they'd need accurate timekeeping. How long was Bjorn's shift today, and how much shall I pay him? When is the shipment of ores supposed to arrive, and when is the shipment of finished tools supposed to leave?


In all honesty, it would make a lot of sense for time to be based on their Circadian rhythms as a species. Even though we humans basically sleep when it's dark and do stuff when it's light, you'll notice that fantasy or scifi writers always lapse back into 24-hour days, with the assumption that roughly half is day and half is night. Sure, it's often handwaved (in the latter) as "that's what time it is on Earth", but even when they do go for an elongated day, you still see it being broken down into our 24-hour sleep patterns.

How long do these races sleep, and how often?

[NRSASD]

If we're talking about a nation that has never seen the sun, that the concept of a surface is as alien to them as a hollow world is to us, the one thing I could see them measuring is tides. Correct me if I'm wrong, but I'm pretty confident that lunar tides affect bodies of water deep underground. That's why Jupiter's moon Europa is probably liquid on the interior. A subterranean culture would notice that their otherwise still lake/sea is deeper in certain areas some of the time, and shallower at other times. You could definitely build a lunar calendar around this even if they never knew why the water shifted.

That or radioactive decay clocks. Or geothermal cycles that we (on the surface) can't detect.

[LudicSavant]

Water clocks, incense clocks, escapements and the like should work just fine underground to measure the passing of whatever units of time you care to use. The real question is what those units would be... what kind of regular cycles would be important to the community in the sense that lunar and solar cycles are important to surface-dwelling earthlings?

Tides definitely still work underground, and tide clocks are a thing. Circadian rhythms are inexact, but some arbitrary period close to a sleep cycle could be chosen (just like measurements of distance were often based on the size of human body parts, even though not every human had the same size body parts). Keep in mind that giant cave systems like the Underdark can have ecosystems and weather, so maybe there's something to use there as well.

[Razanir]

If we're talking about a nation that has never seen the sun, that the concept of a surface is as alien to them as a hollow world is to us, the one thing I could see them measuring is tides. Correct me if I'm wrong, but I'm pretty confident that lunar tides affect bodies of water deep underground. That's why Jupiter's moon Europa is probably liquid on the interior. A subterranean culture would notice that their otherwise still lake/sea is deeper in certain areas some of the time, and shallower at other times. You could definitely build a lunar calendar around this even if they never knew why the water shifted.

Ooh, that's a good idea.

[goto124]

Also, society runs on keeping time to pay your workers every month, to arrange work meetings, etc.

[Razanir]

Update: I can actually keep the 20-hour day and have a tidal calendar, as long as I have a 6-day lunar cycle in retrograde. 6 days is scientifically plausible, having checked with physics majors. And a quick Google search reveals I don't have to care as much about the moon crashing into the planet because it's far enough away. In other words, whether or not the science is exact, I certainly don't need to cop out and say a wizard set the moon in motion.

[5ColouredWalker]

One method I've seen is 'Work Shifts', based on how long people sleep and how long people can work effectively. Given races like Drow, they might have a 16 hour day, 4 slee, 2 4 hour work shifts, and one 4 hour 'free' shift. Others with 8 hour cycles might go 8 sleep/work/other.

[Aliquid]

Also, society runs on keeping time to pay your workers every month, to arrange work meetings, etc.

our culture runs on keeping time. That doesn't mean that all cultures have to. I personally think we are too obsessed with time.

the one thing I could see them measuring is tides. Correct me if I'm wrong, but I'm pretty confident that lunar tides affect bodies of water deep underground.
[snip]
Or geothermal cycles that we (on the surface) can't detect.

Unless there was a massive underground ocean, the tides would be too small to notice. Even on the Great Lakes, the tidal changes are no more than a couple of inches... sure that technically could be measured if that was the only thing changing the water levels, but there would be many other things that could simultaneously change the water levels by a couple of inches…

Geothermal? That's could work really well. Think of "Old Faithful".

Water clocks, incense clocks, escapements and the like should work just fine underground to measure the passing of whatever units of time you care to use.

If there is an underground river, you could easily rig up plenty of water clocks. That would likely be the most common “clock” that people use.

[nyjastul69]

I don't think I've seen candle clocks mentioned yet.

[Studoku]

How about a clock?

Seriously this isn’t that hard. A clock, even one wound arbitrarily will accurately keep time until it winds down. It’s not too hard to imagine a clock tower in the center of a dwarven hold or some such that is wound at the same time daily. make the people in charge of winding the clock up some sort of special order of monks or something.

I think Menzoberranzen has one.

[LudicSavant]

I don't think I've seen candle clocks mentioned yet.

I mentioned incense clocks, which are basically the same thing.

[NRSASD]

The big problem I see with water/mechanical/candle clocks is that if something interrupts them then we can never know even remotely how much time is lost. On the surface, we have the sun to help us keep track (3 days ago my watch broke) but underground? Nothing. While this isn't a big deal for the individual, it's a huge problem for societies. Shipments arrive too late or too early, patrols are missed or sent too close together, etc.

When attempting to reconstruct just how long the society was without their clock, the best one could guess is how many sleep cycles they collectively experienced, which is a really poor estimate because in the absence of light our circadian clocks fry and we sleep based on our fatigue. In other words, people doing hard work sleep more often than people doing light work, and thus there is no consistent number of sleep cycles among the population. As such, timelines would have gaps like these "562 cycles of the water clock -the great smashing of clocks- 346 cycles of the water clock".

That's why tidal clocks are so incredible in the Underdark. You can look at it even after not checking for months and see where you are in terms of the cycle. Yeah, you'll need to observe it for a while to make sure whether the tides are rising and falling; and yes, you'll need an accurate timeline of how the tides look over the course of the tidal year, but it's entirely feasible. The Mayans had absurdly accurate lunar and solar calendars without using telescopes, so it's well within the realm of possibility that if you leave a society alongside a large lake for a couple centuries they'll have mapped out the tides as well as they can. There will always be inaccuracies and it does require a large body of water, but it can serve as a natural, accurate clock that will continue to function so long as the moon exists; regardless of whether life is around to measure it.

Personally, I think the tidal clock is a bit too long scale to serve as the only timekeeping device. It fills the same role as a calendar. Water, mechanical, and candle clocks would be much more useful on a day-to-day basis, especially if the clocks are all synchronized daily corresponding to the high tide; to ensure everyone is on the same time scale.

[AceOfFools]

If we're talking about a nation that has never seen the sun, that the concept of a surface is as alien to them as a hollow world is to us, the one thing I could see them measuring is tides. Correct me if I'm wrong, but I'm pretty confident that lunar tides affect bodies of water deep underground. That's why Jupiter's moon Europa is probably liquid on the interior. A subterranean culture would notice that their otherwise still lake/sea is deeper in certain areas some of the time, and shallower at other times. You could definitely build a lunar calendar around this even if they never knew why the water shifted.

That or radioactive decay clocks. Or geothermal cycles that we (on the surface) can't detect.

The thing about (realistic) tides is that water volume is constant. A sufficiently large body of water will, of course, experience tides, but there needs to be a hide tide in one part of the body of water equal to the low tide experienced elsewhere.

Not that it's a bad idea--it's exactly what I used when designing an underground social system. It also allows really cool things like waterfalls that only exist at certain tides as a low-magic "only accessible at night" portal. You could also make the inhabitants sensitive to the moon's phase, and allow them to know what "tide" it is without looking at a body of water, or use some device/spell to detect the same.

You could also use the cycles of creatures that, like bats, venture out of the caves during certain periods to seek food only to return to the cave to rest/roost. Even if these creatures inhabit only a small percentage of the total cave ecosystem, their regularity (and the fact that they may be a major source of biological matter to the system) potentially allows it to be used far from the creatures.

[NRSASD]

As an aside about tides, one thing that completely blew my mind (yet makes total sense in hindsight), is that water isn't the only material we can see tides in. The sand in the Sahara desert also shifts around due to the moon's gravity. Granted, it's not nearly as noticeable and the wind has far more impact, but its so cool.

The only downside to using biological phenomena as time measurement is that these phenomena are intrinsically linked to the environment in which they live. One of the main arguments that global warming is having real effects right now is that birds are migrating earlier/later than normal and that plants are growing earlier and longer than ever before. There's nothing wrong with using biological phenomena as a rough guess, but if something strange happens to the phenomena your calendar is toast.

[LudicSavant]

Tidal forces affect the entire earth. And the high tide is on the side of the moon and the side opposite of the moon. Right angles get squished together.

[Totema]

If I recall correctly, in an early-ish edition of D&D, subterranean drow were described as having a form of thermal vision, so they kept track of time by observing the cooling rate of a heated stone. Pretty neat stuff honestly.

[5ColouredWalker]

When attempting to reconstruct just how long the society was without their clock, the best one could guess is how many sleep cycles they collectively experienced, which is a really poor estimate because in the absence of light our circadian clocks fry and we sleep based on our fatigue. In other words, people doing hard work sleep more often than people doing light work, and thus there is no consistent number of sleep cycles among the population. As such, timelines would have gaps like these "562 cycles of the water clock -the great smashing of clocks- 346 cycles of the water clock".

Only initially, in experiments humans have found to settle on a 25 hour 'day' when living with set lighting conditions/no clocks.

[Xuc Xac]

The big problem I see with water/mechanical/candle clocks is that if something interrupts them then we can never know even remotely how much time is lost. On the surface, we have the sun to help us keep track (3 days ago my watch broke) but underground? Nothing. While this isn't a big deal for the individual, it's a huge problem for societies. Shipments arrive too late or too early, patrols are missed or sent too close together, etc.

How accurately do you think that stuff needs to be timed? Before the invention of railroads, "your shipment will arrive in 3 weeks" meant "more than two weeks but less than 4 weeks", and not "21 days".

[fusilier]

How would a race keep track of time if they live underground? I'm thinking a civilization that even if they do go above ground, it's not often or significant enough to need to bother keeping track of the seasons, so they have no solar or lunar cycles to care about.

There's an interesting book called "History of the hour" which delves into the history of human relationship with time and time measuring devices.

I think there is a general tendency to think of time units as things that are "built up" from smaller units: for example, 60 minutes make an hour, 24 hours makes a day. But historically the day was the main unit of time. An hour was 1/24th (or 1/12th) of a day; it was a division of the day, and sometimes not even a uniform one. Along those lines, laborers were paid a daily wage instead of an hourly one.

None of this is terribly helpful I'm afraid. The point is that our timekeeping systems ultimately revolve around this one observable phenomenon. A phenomenon that is regular and cyclical, but not consistent: with the shortening and lengthening of "days" (i.e. period of sunlight) during the year. What kind of other phenomenon would a subterranean race have that would be analogous to a day? I don't have an answer. It may be that a subterranean race might have a very different conception of time that's hard to imagine.

Historically, short periods of time were measured in observable ways. The duration of an earthquake was described as how long it took to say a particular prayer. The bell that announced the end of the midday break was to be rung for the amount of time it took someone to walk a mile -- slowly. They used these kinds of "experiential" measurements of time. So perhaps a Dwarven hour would be the amount of time it takes a dwarf to dig six-feet of tunnel? Once some sort of devices for measuring time exist these can be standardized -- but we only have a way to measure the passage of time, not to calculate some sort of cyclical calendar time. In the example of ringing a bell, an experiential measurement of time describes how long to ring the bell, but not *when* to ring the bell. --EDIT-- When to ring the bell would have been based upon some sort of observable phenomenon, like noon (or an hour after noon).

As far as I can tell, lacking some sort of cyclical phenomenon to observe (that's not too long like a month or year), a subterranean race would have to build-up some sort of "day" from other time units. If something disturbs the pattern there may be no way of resetting it, as others have noted, meaning they might have to accept a more flexible calendar.

[SethoMarkus]

Only initially, in experiments humans have found to settle on a 25 hour 'day' when living with set lighting conditions/no clocks.

Thank you, I was wanting to say the same thing but read until the latest post to make sure I didn't repeat what someone else said.

That being said, I think two big questions you need to answer first are:
1) Is a standard unit of measurement used between cultures/societies in your setting?
2) Does the underground society have contact with the surface world?

If yes for both questions, why would/wouldn't the underground society adopt the time measurements used by the surface dwellers?

If no for both questions, how important is it for the subterranean inhabitants to keep time? Touched on by several other posters, time keeping is not necessarily essential to a society. If you decide that it is important, what sort of culture/technology do they have available?

If it isn't a clear yes or a clean no for both questions, then what level of cross-cultural exchange do you want?

As far as time keeping suggestions go, I'm a fan of basing time off of essential facts of life for the subterranean dwellers. Perhaps a variable timekeeping, using heartbeats for smaller units, their own circadian cycle as a "daily" unit, and stalactite/stalagmite growth for marking seasons/years?

[goto124]

1) Is a standard unit of measurement used between cultures/societies in your setting?
2) Does the underground society have contact with the surface world?

If yes for both questions, why would/wouldn't the underground society adopt the time measurements used by the surface dwellers?

Why do we have Metric/Imperial units, left/right side of the road, etc?

[Razanir]

That being said, I think two big questions you need to answer first are:
1) Is a standard unit of measurement used between cultures/societies in your setting?
2) Does the underground society have contact with the surface world?

If yes for both questions, why would/wouldn't the underground society adopt the time measurements used by the surface dwellers?

If no for both questions, how important is it for the subterranean inhabitants to keep time? Touched on by several other posters, time keeping is not necessarily essential to a society. If you decide that it is important, what sort of culture/technology do they have available?

If it isn't a clear yes or a clean no for both questions, then what level of cross-cultural exchange do you want?

The idea for my campaign: You know the trope Sealed Evil in a Can, and how it's normally the backstory? This time you're those heroes who sealed the evil away in a can to begin with. So as part of that, I'm trying to make the world feel younger and more mysterious. To that effect, I'm restricting their choices to humans (or maybe halflings) from one part of the world, bringing in variant rules to make language be more of a barrier, and putting more thought into different cultures. So to answer your questions:

1) Not any more than is natural. So on the surface, everyone will use the day because it's an obvious way to keep track of time, but other units might not be as standard.

2) They might have some contact, but not significant enough to care about solar and lunar cycles for timekeeping. Especially because dwarves have darkvision, so they don't care if it's light out or not when they need to go aboveground.