Worldbuilding 201: Calendars
Greetings and Siccar! ...You know, I am very often that! Some might say I am that too much! But welcome to this year's last blogpost. Anne and I will do an end-of-year post after New Year’s. For today’s blogpost, however, I will do something in honor of today's special day, Winter Solstice!
Namely calendars!
Definition
As always, we start with a calendar… I mean definition!
A calendar is a method to keep track of and differentiate days in a semi-cyclic manner.
Yeah, I am not talking about a physical calendar; I am talking about the abstract calendar! And really, if you think about it, what differentiates a Sunday from a Wednesday or even a Tuesday? Nothing! It is a completely arbitrary distinction between the days.
The beginning of calendars
Let us ask us the question: when did the first calendar come about? It might be tempting to say that it started with agriculture, and there is some truth to that. But the earliest calendar would be best described as during the hunter-gather epoch of species development. That is due to both the hunter and gather part. If you are gathering berries, fruits, or plants, then you need to keep track of when they are good and when they are bad. Sure, you don’t need super specific days to pick and find fruits and plants at spots, but rough enough. So one can say that the earliest calendars were really season tracking.
That is, however, just incredibly rough. The more detailed tracking of days and such really does start with agriculture and the hassle that involves. That is because during hunter-gatherer times, if your berry bush is empty and you misjudged the time, it is no big deal. You just go and hunt some instead, and life is no worse off. With agriculture, a month off with sowing and your plants don’t grow enough and your family and group might now suddenly be STARVING, or even worse, STARBING! That is worse, isn’t it Anne? (Anne: Nooooo! Not the precious planties! How could you miscalculate like that!) Yeah… That is because agriculture is a lot of work, and if you are doing that, you don’t have too much time on your hand to hunt.
Physics in calendars
A lot of calendars have existed in human history, but a few things has recurred many times, and they are all based on physical properties of our solar system and planet. The most obvious one that has been used is the orbital period around the sun. Can you guess why so many societies focus on that? Because that decides the season and when to plan things! We are back at where we have to make sure we do not starb!
But it should be noted, however, that in areas where the seasonal differences are not that extreme in terms of temperature and when things can grow, such as closer to the equator, the care for the orbital period, aka a year, were often greatly diminished even for agriculture. In a lot of places with domesticated plants, you could plop it down any time (or close to) and it would grow just fine, maybe not optimally but it would still grow and give what you want.
While further north/south, closer to the poles, sometimes a week’s or two’s error can mean that the harvest will be a failure. So naturally having the time of the year is way more important near the poles than near the equator then. This assumes of course a slight tilt to the axis of your plant relative to the orbital plane. If your planet has no tilt, the time of year means absolutely nothing as the amount of incoming sunlight never changes. On the other hand, if you have an extreme, like Neptune, where it is almost 90 degrees, a calendar might not be that important either because you literally start seeing the sun all of a sudden when it was gone for months on end or it has now disappeared.
Then, we have, of course, things that can orbit the planet itself, called satellites or moons. For humans on earth, it is the Moon, or Luna. and here we have a culturally interesting thing with the part of not being tied to the orbital periods. Some cultures have focused on what is called the Lunar year over the Solar year exactly because they are not tied to how the planet moves the sun. And you can of course have more than one moon, and then ask, which ones means what to people? Do they focus on one, both, how do they do?
In general, those are the 2 big physical things a calendar would focus on: what the planet orbits and what orbits the planet. Though if you do a bisolar or trisolar system, it can relate to also how the other suns behave as they would clearly observe that as well and want to keep track of, depending on the culture.
Arbitrariness in calendars
I have said it before and I will say it again, culture is everything! When it comes to how society works, the culture is what dictates, not physics. There might be constraints set by physics, biology, and such but cultures are never dictated by it. Like I did in my matriarchy vs patriarchy blogpost, biology might dictate your body, but that does not dictate how you will behave and what role you take in society. Culture does that, and culture is, if anything, arbitrary.
And calendars are no different. For example, why is there 7 days in a week? There are a lot of reasons and stories and things said about it. Some says it is psychology that 7 is just one that feels right to us, which I dispute based on the fact that it feels good because it is familiar. Others say it is because it fits the phases of the moon…an orbital period of the moon is not exactly 28 days and a phase of the moon is also an arbitrary division. So in reality, the 7 day week is an entirely arbitrary decision that was made at some point in history, with maybe some physical influence based on other arbitrary decisions, and then just stuck around.
Then we can take the mayan calendar, which had 20 day names and 13 numbers, to simplify it, giving a cycle of 260 days, I know multiplication! Combine this with the year and you got something like a 53 year long cycle. But those first two things are entirely arbitrary. The 20 named ones likely come from the fact that they had base 20 counting so it reads like 10 to them, but that is in of itself an arbitrary decision and not tied to anything physical.
In all honesty, it is in the arbitrary parts of a calendar that a culture's values and views can shine through because these arbitrary decisions are made based on what is significant to the culture. If we are to take some examples from my universe, the limaces have 13 colours to themselves, which means that 13, or 169 for 2 colour combos, are numbers they are likely to pick so that it matches how they view themselves and their place relative to each other. My Raixher have 8 fingers and 3 sexes, or historically 3 big genders, so they are likely to pick either of those or maybe the product, 24, to fit. (Anne: In the Imperial Saga, the Kaehlari have 1 ice goddess who has 3 daughters representing the three peoples of Kaehlar, but they live in communities where exile is essentially death due to the harsh climate, so 1 is considered extremely unlucky, while 3 or 4 or the resultant 12 are commonly found in different cultural elements).
Which means that they might have a 11 day week. I had a culture that actually did have that. No special reason back then, I was young. But their week was 4 days of work, 1 day off 4 days of work, then 2 days off. Just to illustrate how fundamentally arbitrary it is.
Out of sync calendars
In some ways, calendars can get out of sync, both physical and cultural. In the beginning, people had counted that the years length on earth was 365 days. Which is all good, count that, and you are back to where you started. Except the orbital period is under no obligation to fit neatly to the rotational period of the planet, and lo and behold, it wasn’t on Earth. So they recalculated it and found that it was in fact a quarter of a day longer than 365 days.
So they came up with the genius plan of adding a new day every fourth year so that on average, the year is right. Less than a day wrong won’t harm plants or the like. Though if we count months, the lunar orbital period, of 28 days, we get 13 months in a year..but that is only 364 days and doesn’t fit. How would one compensate for that? Honestly, in the roman empire they kind of went “Sod it” on the lunar calendar and focused instead on the moon being about 29 days and then got 12 months which is even more wrong. And then the amount of days became entirely arbitrary, but they did have, I think it was like 5 days or so each year that were “month-free”, meaning they belonged to NO month. So they just had those extra days to get the months to align up again.
Which is one way to solve it when the thing is arbitrary and cultural. Stuff in days to make it match! But if it is physical, like the 28 days a month thing, you will have to have those two go independent of each other. Which does have the benefit of creating enormously long cycles; well, just long cycles. Like the Mayan one is 53 years, slightly shorter than a human life span. If you had a relatively small society and had a cycle that was 80+ years long, you could have it so that the people are literally named based on the day in the cycle they are born! Or there are only specific names you can give the child then… I need to make this a reality.
The point here is really that physically fixed calendar components cannot be altered to fit each other if they do not neatly fit each other already. Only arbitrary components can be adjusted to fit physical components or other arbitrary components.
Names and numbers in a calendar
The week days are named, but the month days are numbered, yet the months are named, and also numbered, but years are numbered, so how do you decide on these?
Honestly, this falls into the arbitrary category as that is just a preference, but a rough rule of thumb is this, less than 15 gets a name, more than 15 gets a number. This is, of course, not an absolute thing and can easily be broken, but why this is a thing is that remembering a lot of names at the same time for things is a lot of mental work, but numbering them up is easy once you learn to count as a child.
And hybrid systems can easily exist. In western cultures, years are ONLY numbered, but in some historical, and contemporary, eastern cultures, a year has had a number and a name associated with them. Typically the name of the current ruling dynasty along with the number since their reign started. Some have gone even so far as just counting the current ruler so their name changes are much more frequent..
On the names, a small pet peeve of mine is this: in scifi and space operas, they sometimes use “cycles,” and it just means… day. Please don’t do that. If it is a day, or rotation period of a planet, just… call it a bloody day. If you are going to use cycle, have it actually mean something else. Like in my setting, Stellima, I use the word cycle, but that is an administrative unit of roughly 10 days. It is that length because they count in base 10 and 10 days is roughly long enough for relevant things to happen.
Dominance of a calendar
This ties back to both culture and power], but what calendar becomes dominant depends on a lot of factors. Once it is established, it is difficult to get rid of, but which one is used in what context depends on which society has the power, or had the power at the time of it being cemented.
In the real world, the Gregorian calendar with common era year count where we are now wrapping up year 2025 came to dominance because of how Europe colonized the rest of the world and either brought it with them as settlers or at gun point to those they conquered. And now that it is established as the baseline, it is incredibly difficult to get rid of it. Everyone knows this calendar now, so it is easier to default to it. No one knows, outside of their native regions, the other calendars that exist.
So when one calendar is used, imagine: why is it the dominant one? What happened to the old ones? What power was it that caused it to become the dominant one?
Micro-practicum: Stellima Universal Calendar
As I said, in Stellima, they use cycles as an administrative unit of time. The day is based on one of the Concert home worlds, Limpolis, because it has wielded so much power historically even though it has not conquered people. Given that the cognisphere originates from them, and it is what keeps track of time, it makes sense their time is prioritized. Though don’t let this give you the illusion that it is what everyone uses alone, each star nation still have their own calendars that they use.
So the day is based on a Limpolis day, but a cycle is 10 days long. Then they have a “month” that is 3 cycles long, and a year that is 36, aka 12 months long, to the dot. There is no shifting and changing like leap years or the like. And these are, beyond the length of the day of Limpolis, entirely arbitrary and were picked for conveniences in interstellar calculations rather than convenience locally.
This is why a lot of time keeping have multiple modes: one is the unidate, as it is called, and one is the local counting with days, weeks if they have them, months, etc. So if you are going to go out and travel and enjoy life with aliens, you better be used to a lot of time keeping, even though there is one unified interstellar one that is used in legal, interstellar, and political situations.
So you can, and should, have more than one calendar present.
Summa Summarum
And we are at the end. When you make a calendar, keep track of what is arbitrary/cultural in the calendar, and make sure it does reflect the values of the people that uses it, or at least the values they once had, even if you will never tell it. And keep it separate from the physical components. The arbitrary ones can be bent to fit the physical, but which physical ones you focus on depends a lot on where and how the society lives.
Like we celebrate winter solstice, also known as Christmas these days, because in the Germanic regions where it originates, there is a big difference between winter and summer, and this is the darkest day of the year. Now, it will finally get lighter! So happy darkest day everyone! Merry Christmas, happy holidays, god jul, and happy new years! 🙂
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Copyright ©️ 2025 Vivian Sayan. Original ideas belong to the respective authors. Generic concepts such as various types of Earth calendars are copyrighted under Creative Commons with attribution, and any derivatives must also be Creative Commons. However, specific ideas such as Limopolis and the cognisphere and all language or exact phrasing are individually copyrighted by the respective authors. Contact them for information on usage and questions if uncertain what falls under Creative Commons. We’re almost always happy to give permission. Please contact the authors through this website’s contact page.
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