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How To Make A Calendar For A Fantasy or Sci-fi World

Drawing of Stonehenge.
Stonehenge. Okay, it's been debunked that it was for keeping time, but hey - Rule of Cool and all that.

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:


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


The sun and moon.
Behold! The two favourite pacemakers of ancient calendar-designers the world over (often in tandem).

Moon

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.

Emperor sitting on a throne.
Some calendars use the reigns of rulers as usable periods of time.

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?

A robotic clock. Actually, a digital calendar on a circuitboard.
Yep, I know, it's not my best work. The clocky bit's supposed to show the month of the year, and the number below, the day of the month. Don't judge it too hard.

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:

Other Things to Consider


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

A herd of reindeer wandering in the tundra.
Looks like it's reindeer season!
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!