I am looking for ways to tell time when the sky is completely blacked out all the time.

I am aware of nails and other metal objects inserted into candles. Due to vegetation dying due to this calamity, sources of candle making materials could be in short supply. Such as: bees, animal fat,uhh human fat.

Magic is rare, but available, to alleviate some problems.

Godly given magic is also a rare commodity as worshiping souls are becoming more and more rare.

EDIT for clarification

Cause of blacked out sky: Super-volcano event causing an ash-cloud that will last years, maybe decades. After which an ice-age will begin.

Crops, animals die or are eaten. Villages without walls or militias are preyed apon by creatures and other villages.

Travel is risky due to ash-storms (tornadoes of abrasive ash) and creatures/brigands that prey on the traveling caravans. Caravans now use a herd mentality. "They can not get us all.."

Using torches/fires also ill-advised as that is a beacon to said creatures/brigands.

People reactions to:

  • Mages: Untrusted but needed as they bring firepower. Scapegoated by others as cause.
  • Priests: varies from saviors as they can still provide some meals, to zealots as godly magic is becoming more and more scarce as worshipers die off. Some have demanded only those who worship the local deity be allowed services. Think salem-witch trials stuff
  • 3
    $\begingroup$ A similar question that will provide good insight (trust me) is What devices would people use to tell time on a tidally locked planet?. I don't believe it's a straight duplicate, but I wouldn't be surprised if its answers didn't answer this question. $\endgroup$
    – JBH
    Commented Jun 13, 2018 at 16:31
  • 2
    $\begingroup$ Complete black out, accompanied by acid rains from volcanic soot mixed to the atmosphere. Everyone will die. Measuring time will be the last of their problem anyway, while they struggle to eat as the chain food collapses all around them. Soon people will be reduced to eat animal cadavers, then human corpses, then what's left of the grass. HUNGER will mark their time. $\endgroup$ Commented Jun 13, 2018 at 18:55
  • 2
    $\begingroup$ Does this have to be tied into the old clock, or is it allowed to deviate? If I was living underground/under an ash cloud for several years, I'd eventually stop caring whether the sun I can't see is out yet or not. $\endgroup$
    – chif-ii
    Commented Jun 13, 2018 at 20:00
  • 3
    $\begingroup$ If there are no visible natural cycles, why do your people need to know the time? I mean obviously there will be reasons (duration of a spell seems the most obvious), but it seems like you'd need to work out what those reasons are, and any time system would be built around those needs and put that info into this question. The stuff familiar to us is generally designed to work out where you are in the daily and seasonal cycles, and they wouldn't need that. $\endgroup$
    – T.E.D.
    Commented Jun 13, 2018 at 20:04
  • 2
    $\begingroup$ @T.E.D.: Indeed, I had the same thought. We invented timepieces precisely because we constructed a society in which it was a useful thing to be able to meet someone else at a particular place at a particular time with some accuracy. We invented calendars because knowing when to plant and when to hunt and so on is useful. What characteristics in your fictional society require people to know what time it is? If there are none, then it doesn't matter. $\endgroup$ Commented Jun 13, 2018 at 21:04

13 Answers 13


It seems that what you are after is a water clock. There's many designs, but the simplest is a water-filled jug in which floats a shallow bowl with a hole drilled into the bottom. Water trickles into the shallow bowl, until eventually it sinks. This provides a consistent and repeatable measure of time.

  • 5
    $\begingroup$ Very true, although I'd assumed something else was ensuring this sunless world was warm enough for human habitation*. Otherwise the inhabitants have much greater problems to solve than telling the time! (*typing that it's occurred to me that there are plenty of places warm enough for human habitation that are dominated by ice. Using seawater might help in the arctic for instance). $\endgroup$ Commented Jun 13, 2018 at 16:00
  • $\begingroup$ Super-volcano event resulting in an ash-cloud that may last years or decades. Liquid water is available, muddy perhaps due to ash. Ability to create fire is still available, perhaps not the most safe thing as it would be a beacon to creatures that used to only be active at night. $\endgroup$
    – BCwhale
    Commented Jun 13, 2018 at 16:08
  • $\begingroup$ @BCwhale If you could edit that information into your question, that would be very helpful. It would be seen more easily there, and in any case, comments aren't guaranteed to be permanent. $\endgroup$
    – F1Krazy
    Commented Jun 13, 2018 at 16:12
  • 2
    $\begingroup$ Salt and / or alcohol could be added to the water to keep it from freezing. Some oils might be used as an alternative to water, if your people could find / produce them. $\endgroup$
    – jpgo5000
    Commented Jun 13, 2018 at 16:49
  • $\begingroup$ Note that impure water (e.g. seawater) is likely to corrode any machinery which it comes in contact with at a much greater rate than pure water. $\endgroup$
    – Kevin
    Commented Jun 15, 2018 at 5:44

Tide chart.

The moon is concealed. But it is still there. The moon pulls on the sea and causes tides. The times of the tides are known.

http://www.mvtimes.com/community/useful-information/tide-charts/ enter image description here

Tide charts predict high and low tides for a given place well into the future. If you ran out of days, you could start with a tide chart for current days and extrapolate into the future.

It turns the tide chart on its head. You can pay attention and mark high and low tide. Usually you know the time and so look up the tide. Here you know the tide and use it to look up the time.

  • 2
    $\begingroup$ I am not sure that tide tables, were available in medieval times. A quick google does not find anything prior to around the 1800's $\endgroup$ Commented Jun 13, 2018 at 17:51
  • 26
    $\begingroup$ Take this one step further. Rather than basing time off of the sun, base it off of the tides. Low tide is noon/midnight, High tide is morning/evening or vice versa. Human circadian rhythms are slightly longer than the solar day anyhow, and if you never see the sun, why do you need to know when in the solar day it is? $\endgroup$
    – chif-ii
    Commented Jun 13, 2018 at 20:10
  • $\begingroup$ @chif-ii I like that a lot. $\endgroup$
    – Willk
    Commented Jun 13, 2018 at 20:47
  • $\begingroup$ @chif-ii not all bodies of water experience the same amount of low tides and high tides daily. Also, the high and low tides don't happen at the same time of day everyday with a 24 hour day. It could work but not beyond regional use and would not be great for humans who already have an "internal clock" for 24hr days. This site has good info on tides. oceanservice.noaa.gov/education/kits/tides/tides07_cycles.html $\endgroup$
    – Aubreal
    Commented Jun 14, 2018 at 13:38
  • 4
    $\begingroup$ @AlexandreAubrey Using "high tide" as your midnight/noon means that your days aren't a consistent number of seconds - but "one hour" used to be 1/12 the time from sun-rise to sun-set, and that varied from summer to winter. Medieval timekeeping just wasn't that accurate. $\endgroup$ Commented Jun 14, 2018 at 15:26

You can also use an hourglass, filled either with sand or water.

It tells you the passing of time, and if you have enough of them, with different sizes, you can also tell multiples of a base unit of time.


Medieval time measuring is a topic in itself - a very dense one. First of all: forget what you know about time now. In medieval times one did not measure in minutes or seconds, at best in hours, if at all, and then usually to indicate when to meet or because of religious reasons (the "horen" or hour prayers for example). If one needed shorter time measurements, it was usually to make a speed pickup, like aboard (to calculate distance traveled), or for some tournament, training or tactical reasons.

Let's for the sake of the argument, assume that our people are cave dwellers or in an otherwise dark but not freezing environment. No sky to speak of, no animals that generate lots of fat. However, in the dark, mushrooms grow. Not all bioluminescent funghi do glow evenly at all times - some could be used to judge a general "before noon" "afternoon" and "night".

Then there are bioluminiscent insects with a known pulse span, but that is only good for short terms. Like "10 pulses" for measuring the time it took McGuffin to get from the door entry to the couch.

That's it for "living" clocks, but let's see if we can get other ones...

The famous water clock could work: a basin is filled and then water flows out at a known rate, and the basin is refilled. we know that the upper hours have a little more volume in regards to the water contained (more water = higher pressure = higher flow rate), but that can be adressed for by checking that against an hourglass in the making. Which is another method.

But we can modify our waterclock to use a thin tube and a well refined, thick fluid like oil instead and then fill the lower basin back up to the reservoir at specific times. That would be an oil clock.

But as we have oil, maybe crude oil or naphta, we could also put a whick into the oil tube with a swimmer, and then ignite it. The oil will burn at a slow rate, and lower the level slowly - if measured out correctly, this could give good measurements over long periods of times, maybe even several days to a week within a somewhat ok space.

But let's go mechanical! Our cave people might have a source of flowing water (that is, unless the dark sky is eternal winter, then... forget time measuring at all, you don't need time in the wolf-winter before Ragnaröck), which should be steady enough. If water flows, it can move a waterwheel, like from a watermill. Using this power source and a few gears, one might make a simple clock that turns the hour indicator once or twice a day, maybe even some other dials that indicate it is working (minutes), before or after 'noon', day of the week, phase of the moon etc.


There's no real reason a normal clock wouldn't work. The oldest clocks are over 1000 years old, and they can be built with simple tools if they are large. https://en.wikipedia.org/wiki/Clock#Early_mechanical


A large pendulum could do the trick such as Foucault’s Pendulum. In addition, various mechanical timepieces using pendulums from the old-style grandfather clock to a cuckoo clock, to spring driven devices.

Candles could also be used with hours marked off as they burn.

Incense clocks would be another way as well.

  • 1
    $\begingroup$ Foucault's Pendulum was my first tought too $\endgroup$
    – Kii
    Commented Jun 15, 2018 at 8:45
  • $\begingroup$ Complex clockwork mechanisms such as pendulum driven clocks were only invented past the renaissance, the most early clocks of mechanical design stem from the 1200s $\endgroup$
    – Trish
    Commented Jun 17, 2018 at 12:33
  • $\begingroup$ @Trish the technology was there to use them, given the existence of the [Antikythera mechanism]{britannica.com/topic/Antikythera-mechanism) mechanical clocks are not out of the question. Much Roman and Greek knowledge was not lost during the dark ages, merely isolated. $\endgroup$
    – user20762
    Commented Jun 17, 2018 at 17:04

We're making a whole new world here, right?

The Land Speaks!

Each day is split into four phases.

"Dawn": During the time that the sun would have risen, a priest feels a sudden surge of excited energy. It causes a hastening of his actions breaks him from slumber. This speeding up is something they call the Fastbreak. He receives new energy from the deity and can produce food. This energy diminishes through the day.

Midday: The animals become suddenly enraged and attack. They all seem to let out a sudden collective howl as something inside of them causes them to lose control of their senses. Nobody wants to be out during this time, especially alone. They call this time NoOne Time.

Evening: The mages feel a sudden surge of energy replenishing what they have used through the day. Suddenly the air crackles like lightning, followed by a humming noise that you can't get away from. It's hard to talk over the din because even plugging your ears doesn't diminish it much. This time is called DinEar.

Nighttime: The land feels a sudden surge of energy. The volcanoes become much more active and will emit a sudden BOOM signalling this time. New ash, smoke, and a black glowing mineral cover the area. The mineral is of very uniform grain size, making it perfect for hourglasses. They call this mineral Black Ash Minite.

Priests and Mages know to pace themselves on the use of their energy. They can FEEL it leaving them. Since NoOneTime is the most dangerous time of the day, mages have to be especially careful not to deplete energy overnight on frivolous magic lighting or heat. It makes for a nice tension point for nighttime magic use.


You'd need one of the rare and extremely valuable sunstones! Even through cloudcover and smoke, with holding a sunstone towards the sky will tell you at what azimuth the sun is, making it possible to track both time and date! Important happenings such as solstice or mid winter "blot" can be ascertained by knowledge and a sunstone.

The priests naturally hoard them, as it lets them keep track of the important religious dates, the mages covet them for they need precise timing for their occult rituals. Ensue chaos and war ;)


There its a plethora of ways to do such thing, from water clocks to sand clocks, gravity clocks (they sound fancy but they are just falling stuff over time) in general have existed since always, time its relatively easy to keep track, but if you are looking for some magical/medieval cool kind of clock you could do a buffed solar stone, vikings used to have huge quartz stones as a magnifying glass to see the sun under the thickest fog then they used it to cast a shadow into solar clocks to tell time and to orientate themselves, so if there's magic you could do some kind of buffed solar stone that helps you to find the sun even through the ashes to do the same, to orientate yourself and to tell the time.

Ps. also eruptions usually throw lots of quartz to the air, specially powerful eruptions


A Fire clock within a building / opaque lamp will set you up - fire needs tending to or it goes off, you know.

In a world without the sun to provide natural light and heat, someone has to be in charge of maintaining the community's artificial light+heat source - let it be a big firepit in the village's main hall (Viking setting, anyone?). Inside of a building, you're not exposing your village to Night Shades/brigands of the Dark.

Since a bunch of people rotate to be in charge of this socially important task, and they need to keep track of when to place extra wood into the fire (wood is also scarce because, umm, no sun for trees to grow properly), the Great-pit, where everyone gathers to warm up and cook and eat (also, in a medieval setting it's easier to get your fire from an already lit one) is a good place to get your time reference.

When venturing out, use an opaque lamp and measure time by the amount of fuel remaining/size of flame (that's affected by the amount of available fuel)


Possibly some people have the condition chronometria, an innate ability to detect the passing of time much more accurately than most people. The condition is somewhat rare, and before the disaster occurred, those who had the condition often found employment on ships or in mines. Some chronometriacs found a religious calling, and provided accurate timekeeping services to monastic orders.

After the disaster, the unusual condition becomes more valued, possibly even leading to an order or guild of timekeepers.

The exact mechanism by which chronometria works is perhaps unknown, but theories could include an unconscious awareness of one's own heartbeat, sensitivity to influences from the heavens, divine inspiration, and witchcraft.


Personal biological signs could be used. Breaking the day into a number of small meals with society agreeing to try to all eat together. The day might be split into 5 parts, around 4 meals.

  • $\begingroup$ Four meals makes four parts. And the circadian rhythm is not very accurate. $\endgroup$ Commented Jun 14, 2018 at 1:49

Ynneadwraith's answer got a lot of support as a most obvoius one (I upvoted it too), yet it's not accepted... What are you waiting for? Some "magical stuff"?

Here you go:

  • Some "predcestors'" left artifacts. This can vary from monoliths to lost watches. Artifacts don't even need to tell the exact time, just to change their state with constant periodicity. "Oh, Sarah, haven't seen you for eleven thetas".

  • Sense of time of commoners. A racial feature - they just perfectly know, how much socks they could've knitten (the second/minute/hour is just a human invention) since their last meeting with their buddy. "Oh, Sarah, haven't seen you for an entire two thousands socks"

  • Some other regular event (like regular earth tremors or smth.)

The main question to you is "Why would they want to measure the time in such an unpredictable world?"


You must log in to answer this question.

Not the answer you're looking for? Browse other questions tagged .