How To Make A Calendar For A Fantasy or Sci-fi World
A calendar is a time-measuring framework, designed to provide context over any span of time from days to years. They’re pretty ubiquitous, although the way they’re designed depends on a variety of factors: how do the people use their time? What do they need most – a reliable source of food? A framework to boost a sense of community? A way to organise a routine-driven life, such as a 9-5 job?
A Calendar’s Vital Ingredients
A calendar needs a few things:
- a pacemaker, to keep a regular rhythm
- days, because people tend to find those quite useful
- a practical naming/numbering system for days and months.
Natural Pacemakers
As with most cultural details, civilisations use what they have in order to get what they need. So let’s start this post with a look at how they make sure they’re marking time properly. What are they using as their calendar’s pacemaker? The most common pacemakers here on Earth are the sun and the moon. Each of these has pros and cons:
Sun
- Pros: The sun causes our seasons, which gives each time of year its own unique set of characteristics. This makes it easy to identify a longer term cycle (such as a full year) and identify if a day is earlier, or later in the year.
- Cons: Some days are longer than others. Our planet is tilted on its axis, and one orbit around the sun is 365 days and a bit. Day length also changes depending on your latitude. Both of these facts make our orbit around the sun somewhat complicated. Averaging out the lengths of our days for calendar purposes is a tricky feat.
Moon
- Pros: Phases remain a constant 28 days throughout the year
- Cons: Every moon phase is the same (with a few irregularities such as blue, blood, or supermoons), making it hard to break the time down further or define when the end of a year is. It also helps if you can actually see the moon at some point
- Misc.: The moon affects several rhythms in the natural world, such as the tides. These can be used to effectively make a lunar calendar.
The sun and moon offer complimentary strengths for calendar design. For this reason, many calendars are “lunisolar”, meaning they use both. The Islamic calendar is an example of a purely lunar calendar.
Other Pacemaking Options
The sun and moon aren’t the only options, especially for fantasy and sci-fi projects. Let’s check out some alternatives.
- Stars: The Ancient Egyptians measured the start of the year by the appearance of the Dog Star at sunrise. This coincided with the annual flooding of the Nile River, which made the star's appearance a meaningful marker.
- “Regnal” years: This is where the reign of a given emperor/empress or monarch is used as a specific span of time.
- Arithmetic calenders: Whether a computer does it or a biological being, if someone’s counting time purely to maintain a calendar, then it’s an arithmetic calendar. Though honestly, it feels like this name is applied more to human-maintained calendars than robot-maintained. Example: the Jewish calendar. Arithmetic calendars have to be adjusted for accuracy from time to time. Given the link between timekeeping and faith, the administrator may encounter pushback when making those adjustments.
- ‘Soft’ seasonal markers: Might your civilisation mark the start of autumn when the first leaf lands within the chief’s court? Or when the first bear is spotted fishing in the river? Americans do a version of this with Groundhog Day.
Leap Days
Like I said earlier, a single, complete rotation around the sun (called a “tropical year”) lasts for 365 days and a bit. That “and a bit” needs attention, otherwise the calendar will start getting annoyingly inaccurate after a decade or two.
It took humankind a while to nail this. The Julian calendar was based on the (only slightly) incorrect assumption that Earth’s orbit takes 365.25 days. The Gregorian calendar, one of the world’s most widespread calendars, adjusts for this. Please don’t ask me how, I break easily.
The inclusion of a leap day is called intercalation. Not all cultures are content to make such adjustments, with Islam being the most notable example. Rather than adjust, the Islamic calendar is kept up to date with ongoing observation of the sun.
A side effect of keeping the year in line with our experience of the sun, is that it divorces the calendar’s relationship with the moon: 365.25-ish doesn’t divided exactly into 28 days, so the months go out of sync. This is why the months of the Gregorian calendar are usually not exactly 28 days: that length of time is now treated as a suggestion rather than a rule.
Modern Calendars
Given the early-civilisation tendency to use the sun and moon for calendar-making, the futuristic minded among you might want a techier alternative. So let’s look at some.
A number of attempts have been made to create calendars that don’t rely on the sun (although they may be modelled on when the sun is up vs. down, since we humans, diurnal little devils that we are, quite like that). On another pragmatic level, most people would probably be quite annoyed to have to switch from the old system to the new one. How will you handle that in your worldbuilding, if a switchover happens at any point?
AI/Purely Robotic Calendars
Some simple calendars have an absolute start date; such a system is called Unix Time. This means they don’t have to keep adjusting to a recurring event, such as a sunrise. This lack of ongoing reference points can become problematic over a longer period of time, and not just for calibration purposes: people would get horribly confused! We’re just not as good at keeping count, as computers are. Would you want to tell your friends you're going on holiday on day 283,395?
Anyway, here are some sci-fi suggestions:
- Regular or one-off special digital events: computers are exceptionally good at doing things like marking time. In a world where computers control most things, might they keep count of time to create a calendar? One writer I know has a story in which an ancient suite of computers were switched back on by a new civilisation. Could that event, with its “day 0” quality, be the basis for a calendar? Alternatively, daily backups, especially for cyborgs or uploaded folk, might be a good alternative to a sunset for marking the end of a day.
- Synthetic ‘moons’: Satellites or similar space-things might appear in the sky at regular intervals, creating a substitute for the moon.
Other Things to Consider
- What’s the calendar going to be used for? Marking a working week? Coordinating social gatherings in a community of otherwise isolationist people? Helping farmers keep their agricultural activities (such as when in winter or spring to plant seeds, when every day looks much like another and the warm weather's nowhere to be seen)?
- What characteristics does the civilisation using the calendar have, that might factor in? Do they hibernate or migrate, perhaps? Do they travel between the stars and sleep for hundreds of years in between?
- Might your civilisation use two calendars concurrently? The Eastern Orthodox Church does this: the Julian and Revised Julian calendars.
- What might their calendars look like? Most of us are familiar with paper or digital calendars, but what about something radically different, such as your own version of Stonehenge, or any one of many designs of sundial? Not-so-fun-fact: glass sundials exist and can cause fires.
- What mythology exists around your calendar? The months in our Gregorian calendar have pretty names: January, April, September. Those names have histories behind them. The same is true for days of the week, though strangely, we don't seem to name our weeks.
- For a different spin on calendar mythology, the Ancient Egyptian calendar was divided into 12 months, each 30 days long, which left them with 5 days spare which they tacked onto the end of the year. A myth arose around why those final 5 days existed: The goddess Nut came to Thoth, saying that she had been forbidden by Ra to bear children on any day of the year. Thoth agreed to help her. To do this, he gambled with the moon god Khonsu for a portion of his light. Thoth won the bet, and used that light to create an extra 5 days in the year, in which Nut was able to bear children.
Other Calendars
Most of the information available about calendars focuses on European or Far-Eastern examples, so let's have a look at some alternatives.
African
The Akan people of West Africa have a traditional calendar that marks days, months, and years. It has lunisolar elements, though its workings are quite radically different from what Westerners are used to. Weeks are 6 or 7 days long (depending on how you use the system). At one point, the Akan week was combined with the Gregorian week, and the combination allowed for 42 combinations, which created a form of month. When 9 of these 40-day segments are complete, the year is considered to have ended.
You can find a proper description of how this calendar works, here.
Overall, the Akan calendar is heavily based on social events or creates pockets of time for specific tasks or social events.
Native American
The best-documented Native American calendar is the Cherokees’. It's heavily lunar-based, and mostly used to make social events easier to coordinate. This role was particularly important in ensuring that various Cherokee clans mingled.
The Cherokee, plus a number of other tribes, used a certain species of turtle's shell as a calendar.
Here is a link to a fuller resource of information.
Tundral and Arctic
The days and nights can vary wildly in length near the poles, with the sun not setting for many days at one point in the year, so it’s easy to assume that lunisolar calendars are impractical, but the Inuit did indeed succeed in incorporating both the sun and moon to measure their year.
It's also worth noting that Inuit concepts of linear time were rather different from ours, and that the exact movements of the sun and moon vary wildly within a relatively small distance in the tundra, making a standard calendar for a large region impossible; travel only 100 or so miles in any direction and the days and nights will change in length accordingly, making a need for highly localised calendars.
Inuit calendars are based on seasons and by extension, the food that will be available during those times. As food availability can vary wildly, the opportunity for food festivals arises in times of glut, and with it, the chance to be more sociable. Here is an infographic of a few Arctic calendars.
To Finish
This has been a pretty comprehensive whistlestop tour of calendars, and I hope it’s been useful! As for all these worldbuilding posts, if you’d like to work with me on constructing a calendar for your world, contact me - it's a pleasure to work with you all!
Credits
All art and title image by me!