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They call this day the 11th of March
Who wants to talk with me about interplanetary calendars?
I just finished the old book that's been on my to-finish for ages about the history of calendar reform, and it was surprisingly interesting for a book that consists in large part of quotations from Hansard and League of Nations committee reports (the one about cross-cultural perceptions of time is still on the to-finish for awhile yet, sorry.) They both ended up on that pile after the first time I read Machineries of Empire and was curious about how the calendar-based magic system in that might actually worked. (Mind you I don't think the MoE system can really be specifically calendar-based in its actual mechanics, also the farther I got in the calendar reform book, the less reasonable Cheris's quick-change reform seemed, and it didn't seem that reasonable even to start with.)
But! Calendars in worldbuilding are an interesting thing to think about, and I don't think I've ever seen a system used in a multi-planetary polity that really made sense. You have systems like stardates (that was a deliberate throwing up of hands at the idea of coming up with a workable one) and ones that just copy Gregorian time-words without really putting much thought into it, and not much else. (It's amazing how rare it is to see a SF story that doesn't have a very-nearly-24-hour day cycle, even. Where is the spacelag of shifting from a 30-hour day to a 20-hour day??)
So.
Suggested preliminary reading: Paul Krugman's The Theory of Interstellar Trade. Wikipedia Calendar (and subsequent rabbit hole.) How To Observe Judaism In Outer Space (and subsequent rabbi hole.) Falsehoods programmers believe about time
So there's like basically three things calendars do, right?
--Be accurately aware of an abstract concept of passage of time
--Keep track of natural cycles, or other recurring time spans like growth and speed
--Allow people in different places to do things at the same time as each other
Pretty much every human society has some way of tracking recurring cycles/times, but it doesn't have to be in a way that's obviously recognizable as a calendar. Like, I can tell you how far into Spring we are right now just by which wildflowers are blooming in mowed lawns, and I could probably be accurate based just on wildflower blooms within two weeks from about February to October most years; paying some attention to day/night length just in case, and that would probably give me all the timekeeping I would need for basic agricultural/foraging stuff, and I would remember years based on "The year we had the very cold February and I made maple syrup" and "the year of the earthquake-hurricane" and "The plague year" and so on, which is basically the way I remember years anyway. Even in societies that have a formally-kept calendar, probably most humans have used that kind of timekeeping for most things most of the time anyway.
But keeping an accurate count is also useful, and there are calendars that have been verifiably keeping an unbroken count of days for at least 2500-3000 years (and that's just as far back as we can verify.) It's useful when you really want to be more certain of when to expect something than "Around the time the buttercups bloom", and it means that if for some reason you miss the buttercups one year, you're still good. It's also really necessary for bureaucracy (which is at least as old as written history) - if you want to be able to set deadlines for things like taxes, and enforce them in a way that at least appears fair, you need to be able to accurately give the date. And then eventually of course you need it for science.
And, of course, buttercup-based timekeeping only works in a hyperlocal system. The buttercups will bloom earlier or later even a few days' walk in any direction from here. If I want to be able to say "meet me at the river-mouth when the buttercups bloom," we need to both be able to convert our local buttercup time to the time they bloom at the river-mouth. Even astronomical-based systems can have issues with this, even across fairly small distances - apparently there were court cases in England well into the modern period for rent payments due 'on the day after the full moon is seen' where people claimed they could pay late if it was overcast at their house, even if it wasn't at the landlord's.
Most widespread modern, and recorded premodern, calendar systems combine all of those - they will have a count of time, but will try to connect it to natural cycles, and generally use the count of days and some kind of astronomical cycles as cross-checks on each other. And they will have some kind of correction factors to align the two, and make it work across long distances and different contexts.
There is on top of this, of course, the cultural factor, which is partly that humans put all kinds of extra significance into dates and cycles and calendar-counts; and also partly that once you've committed to a certain way of doing dates, bureaucratically it's just a lot of work to change it even if it's terrible.
SO, thinking in interstellar terms, it seems to me like a human society that was trying to maintain some kind of bureaucracy/science/cultural alignment across light-year distances, or even just on different planets, you would almost definitely end up with at least two timekeeping systems in general use: a local calendar based on local cycles that are important to human life; and a universal system that uses an arbitrary counting-tick that lets two different systems figure out when something happened at the 'same time'.
The universal system would have to have some way of dealing with relativity issues; over interplanetary or interstellar distances you *can't* just keep a count of days, or even atomic clock ticks. It is too late at night for me to think about it too hard, but you would have to have *something* to serve that purpose. Maybe you would need some kind of interstellar landmark like a quasar, where anyone in the galaxy could observe it, know what time that observation shows, and then calculate their distance from it via redshift for a very accurate speed-of-light correction? Or just give up on having any kind of science or bureaucracy that is easily compatible between planetary systems; ships just arrive when they arrive and you treat each system as an isolated island in space-time.
The whole question of timekeeping for spacecraft is big and complicated and already having major consequence for everyday human tech - your smartphone has a relativity correction built into the GPS software.
The local calendars would be based on the same things Earth calendars use: dark/light cycles (lunar? Solar? something more complicated?); weather/temperature cycles (seasonal); water cycles (tides, melts, flood seasons); biological cycles (lifespans, circadian rhythms, reproductive cycles, of humans or other life-forms); astronomical cycles (either tracking the planet's motion in the sky, or detectable movement or changes of other astronomical bodies.) You could imagine other important cycles as well - i.e., a moon where tidal heating caused a regular cycle of geological activity. What cycles would you track in the calednar if you were living on something like a Jovian moon, with a lot more relevant things to track than on relatively simple Earth? How about on a planet with no seasons to delineate a year and no moons to delineate a month - you could still track orbital revolutions via the stars, but would you?
There would also be the question of people living in artificial habitats where any cycles were also at least somewhat artificial. Do most space habitats use the same calendar - is there a standard calendar based on logical math and human biological cycles that is used in deep-space habitats (and presumably planetary ones where there are no local cycles in the right scale for humans)? What cycles other than sleep/wake cycles would be important enough to track? What would we use for a 'year' if we had no real need to use an Earth year? Or is a more-or-less Earth-based one still used as 'standard' when there is no local cycle that can be adapted? Or do they each make up their own based on somebody's private crackpot calendar reform?
If there is a 'standard' calendar in use for artificial habitats and planets with 300-year-days, you'd have to assume parts of that calendar would also become used at least in the vernacular even on planets that had a local-day-based calendar as well. So at that point, most cosmopolitan places would be juggling at least three calendars - the 'standard' space calendar, the universal count of time, and the most important local calendar. Then you'd have to assume there would be at least one or two 'cultural' calendars that were based on some entirely *different* planet's cycles that some people still insisted on using for whatever reasons, and you're up to at least four.
(Four calendars may seem like Too Many, but then I remember as a white american christian, I am regularly dealing with the Gregorian calendar; my work's accounting calendar, which is a steady count of fourteen-day pay periods with a New Year in the summer; and the Christian liturgical calendar, which mostly lines up with the Gregorian except when it doesn't. Also there's the academic year, with all its hyperlocal variations, that still shapes my years even long after graduation; I have enough Jewish acquaintances I try to at least track their holidays (even if I'm super awkward at doing anything with that knowledge); I tend to time my vacations to lunar/tide cycles; and every so often I do something ridic in Excel and fall back on Julian days. So that's more than four. But at least they all use the same length of day/night count.)
Anyway, basically, this is my plea to work that kind of calendrical and timekeeping nonsense into more of your SF. It's fun! I swear!
I just finished the old book that's been on my to-finish for ages about the history of calendar reform, and it was surprisingly interesting for a book that consists in large part of quotations from Hansard and League of Nations committee reports (the one about cross-cultural perceptions of time is still on the to-finish for awhile yet, sorry.) They both ended up on that pile after the first time I read Machineries of Empire and was curious about how the calendar-based magic system in that might actually worked. (Mind you I don't think the MoE system can really be specifically calendar-based in its actual mechanics, also the farther I got in the calendar reform book, the less reasonable Cheris's quick-change reform seemed, and it didn't seem that reasonable even to start with.)
But! Calendars in worldbuilding are an interesting thing to think about, and I don't think I've ever seen a system used in a multi-planetary polity that really made sense. You have systems like stardates (that was a deliberate throwing up of hands at the idea of coming up with a workable one) and ones that just copy Gregorian time-words without really putting much thought into it, and not much else. (It's amazing how rare it is to see a SF story that doesn't have a very-nearly-24-hour day cycle, even. Where is the spacelag of shifting from a 30-hour day to a 20-hour day??)
So.
Suggested preliminary reading: Paul Krugman's The Theory of Interstellar Trade. Wikipedia Calendar (and subsequent rabbit hole.) How To Observe Judaism In Outer Space (and subsequent rabbi hole.) Falsehoods programmers believe about time
So there's like basically three things calendars do, right?
--Be accurately aware of an abstract concept of passage of time
--Keep track of natural cycles, or other recurring time spans like growth and speed
--Allow people in different places to do things at the same time as each other
Pretty much every human society has some way of tracking recurring cycles/times, but it doesn't have to be in a way that's obviously recognizable as a calendar. Like, I can tell you how far into Spring we are right now just by which wildflowers are blooming in mowed lawns, and I could probably be accurate based just on wildflower blooms within two weeks from about February to October most years; paying some attention to day/night length just in case, and that would probably give me all the timekeeping I would need for basic agricultural/foraging stuff, and I would remember years based on "The year we had the very cold February and I made maple syrup" and "the year of the earthquake-hurricane" and "The plague year" and so on, which is basically the way I remember years anyway. Even in societies that have a formally-kept calendar, probably most humans have used that kind of timekeeping for most things most of the time anyway.
But keeping an accurate count is also useful, and there are calendars that have been verifiably keeping an unbroken count of days for at least 2500-3000 years (and that's just as far back as we can verify.) It's useful when you really want to be more certain of when to expect something than "Around the time the buttercups bloom", and it means that if for some reason you miss the buttercups one year, you're still good. It's also really necessary for bureaucracy (which is at least as old as written history) - if you want to be able to set deadlines for things like taxes, and enforce them in a way that at least appears fair, you need to be able to accurately give the date. And then eventually of course you need it for science.
And, of course, buttercup-based timekeeping only works in a hyperlocal system. The buttercups will bloom earlier or later even a few days' walk in any direction from here. If I want to be able to say "meet me at the river-mouth when the buttercups bloom," we need to both be able to convert our local buttercup time to the time they bloom at the river-mouth. Even astronomical-based systems can have issues with this, even across fairly small distances - apparently there were court cases in England well into the modern period for rent payments due 'on the day after the full moon is seen' where people claimed they could pay late if it was overcast at their house, even if it wasn't at the landlord's.
Most widespread modern, and recorded premodern, calendar systems combine all of those - they will have a count of time, but will try to connect it to natural cycles, and generally use the count of days and some kind of astronomical cycles as cross-checks on each other. And they will have some kind of correction factors to align the two, and make it work across long distances and different contexts.
There is on top of this, of course, the cultural factor, which is partly that humans put all kinds of extra significance into dates and cycles and calendar-counts; and also partly that once you've committed to a certain way of doing dates, bureaucratically it's just a lot of work to change it even if it's terrible.
SO, thinking in interstellar terms, it seems to me like a human society that was trying to maintain some kind of bureaucracy/science/cultural alignment across light-year distances, or even just on different planets, you would almost definitely end up with at least two timekeeping systems in general use: a local calendar based on local cycles that are important to human life; and a universal system that uses an arbitrary counting-tick that lets two different systems figure out when something happened at the 'same time'.
The universal system would have to have some way of dealing with relativity issues; over interplanetary or interstellar distances you *can't* just keep a count of days, or even atomic clock ticks. It is too late at night for me to think about it too hard, but you would have to have *something* to serve that purpose. Maybe you would need some kind of interstellar landmark like a quasar, where anyone in the galaxy could observe it, know what time that observation shows, and then calculate their distance from it via redshift for a very accurate speed-of-light correction? Or just give up on having any kind of science or bureaucracy that is easily compatible between planetary systems; ships just arrive when they arrive and you treat each system as an isolated island in space-time.
The whole question of timekeeping for spacecraft is big and complicated and already having major consequence for everyday human tech - your smartphone has a relativity correction built into the GPS software.
The local calendars would be based on the same things Earth calendars use: dark/light cycles (lunar? Solar? something more complicated?); weather/temperature cycles (seasonal); water cycles (tides, melts, flood seasons); biological cycles (lifespans, circadian rhythms, reproductive cycles, of humans or other life-forms); astronomical cycles (either tracking the planet's motion in the sky, or detectable movement or changes of other astronomical bodies.) You could imagine other important cycles as well - i.e., a moon where tidal heating caused a regular cycle of geological activity. What cycles would you track in the calednar if you were living on something like a Jovian moon, with a lot more relevant things to track than on relatively simple Earth? How about on a planet with no seasons to delineate a year and no moons to delineate a month - you could still track orbital revolutions via the stars, but would you?
There would also be the question of people living in artificial habitats where any cycles were also at least somewhat artificial. Do most space habitats use the same calendar - is there a standard calendar based on logical math and human biological cycles that is used in deep-space habitats (and presumably planetary ones where there are no local cycles in the right scale for humans)? What cycles other than sleep/wake cycles would be important enough to track? What would we use for a 'year' if we had no real need to use an Earth year? Or is a more-or-less Earth-based one still used as 'standard' when there is no local cycle that can be adapted? Or do they each make up their own based on somebody's private crackpot calendar reform?
If there is a 'standard' calendar in use for artificial habitats and planets with 300-year-days, you'd have to assume parts of that calendar would also become used at least in the vernacular even on planets that had a local-day-based calendar as well. So at that point, most cosmopolitan places would be juggling at least three calendars - the 'standard' space calendar, the universal count of time, and the most important local calendar. Then you'd have to assume there would be at least one or two 'cultural' calendars that were based on some entirely *different* planet's cycles that some people still insisted on using for whatever reasons, and you're up to at least four.
(Four calendars may seem like Too Many, but then I remember as a white american christian, I am regularly dealing with the Gregorian calendar; my work's accounting calendar, which is a steady count of fourteen-day pay periods with a New Year in the summer; and the Christian liturgical calendar, which mostly lines up with the Gregorian except when it doesn't. Also there's the academic year, with all its hyperlocal variations, that still shapes my years even long after graduation; I have enough Jewish acquaintances I try to at least track their holidays (even if I'm super awkward at doing anything with that knowledge); I tend to time my vacations to lunar/tide cycles; and every so often I do something ridic in Excel and fall back on Julian days. So that's more than four. But at least they all use the same length of day/night count.)
Anyway, basically, this is my plea to work that kind of calendrical and timekeeping nonsense into more of your SF. It's fun! I swear!
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Which makes me wonder if they're measuring two different things- if sleep cycle naturally lags our other circadian cycles for some reason. I haven't found anything where they tested other circadian cycles on people who were freerunning on sleep, or specifically tested whether those other cycles are as effected by light exposure as sleep is.
I used to think I had a longer-than-24 sleep cycle, but if I'm careful about artificial light exposure, that effect seems to mostly go away (though that might also be related to getting older.)
Anyway, yeah, it's interesting to think about at what point off a 24-hour day humans would just give up on working with planetary day!
Some NASA teams that work closely with the rovers have run long-term on Mars time 24-hours-and-almost-forty-minutes, and it has not worked very well, but also they seem to have treated it more like shift work than actually adapting to a different day.
I also have to wonder if people with off-kilter sleep cycles would be disproportionately likely to volunteer for that kind of mission! The only thing is that a seriously off-kilter sleep cycle tends to make it a lot harder to be the kind of person who wins slots on space missions....
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And yeah, with age, I'm definitely starting to get into a more regular 24 h cycle.. but partially I think my room now has worse blinds, so the sun is a major factor in that.
I have joked before that I'd be suited for working on the Mars rover teams because of this haha! But I've only ever heard it as jokes; I don't think anyone on the team has ever commented about it in that way, bc like you said, they don't seem to adapt to it fully (probably to keep synced with non-rover teams?)