Good morning, interweb. Let's Worldbuild!
So last time we created a solar calendar. Watch that video before this one lest there be
confusion because this time we're going to tackle the lunar calendar.
As the name implies, lunar calendars, such as the Islamic calendar, functionally ignore the sun and choose instead track the moon and its phases.
Their major selling point is their ease of adoption. The shorter the period,
the easier the tracking. But they lack the ability to predict seasons because the sun is ignored.
Unlike the sun, which kind of always looks the same, the moon goes through phases during its orbit
so it acts like a celestial clock.
Just by looking at the night sky, you can kinda tell where in the cycle you are. No math required.
Easy adoption.
Given that they don't predict seasons, lunar calendars can work well in areas which experience minimal seasonal variation. Broadly speaking, here.
So using the same planetary system as last time, let's dive straight into the spreadsheets.
Like before, we can drop our planets orbital period here and the lunar period here and the spreadsheet will do its thing.
In the lunar calendar section, we should begin, as always, by ironing out the decimal.
It's dangerously close to 32 Earth days, which is great
Having the month, a.k.a. the lunar period, be a multiple of four is going to come in handy in a bit
so let's go with 32 local days
And for added realism, let's introduce some controlled calendar drift
Let's have a leap month every 20 months, just because we can
adding 0.05 to here means that every month will be 32 local days long,
except for every 20th month, which will be 33 local days long.
And to achieve all of this, our local day will be defined as being
24.26957878 Earth hours long.
Super!
So that's the month done. What about the year?
Like last time our culture will quickly realize that there will be 8 to 9 lunations
a.k.a lunar periods a.k.a. months per solar year
So they'd likely set their year to eight 32 day months
or nine 32 day months, depending on their preferences.
Eight will fall short of the solar year and nine will exceed the solar year. So a pure lunar calendar will necessarily
cycle through the seasons, making it impossible to have seasonal festivals like Christmas.
A winter festival in spring is no winter festival in my eyes
This is a common feature of lunar calendars.
Take Ramadan for example:
It's the ninth month of the Islamic calendar and here is its path through the seasons over a 100 year period
This drift occurs because the Islamic lunar calendar is 10 to 11 days short of the solar year
Thus, lunar calendars could lead to some interesting dialogue options.
And hey, if lunar calendars ignore the solar year and the seasons, why not ignore them in style?
Welcome to the world of ritual calendars,
calendars that favor tracking societal constructs over astronomical accuracy.
Like maybe our culture has a 13-god pantheon and decide to dedicate one month to each god
Thirteen 32 day months and year say, zero fraks given if that's massively out of whack with the solar year
Or maybe they have a set of moral codes they live by
and they dedicate each month to the pursuit of those virtues
Like seven 32 day months: Loss, Gluttony, Greed, Sloth, Wrath, Envy, and Pride,
demonstrating how nomenclature can tell us a lot about a culture. And this may seem crazy,
but we have real-life precedent for such ritual calendars.
One ancient Mayan calendar consisted of a 260 day year,
a full 105 days short of the solar year. We don't know exactly why such a calendar arose
but theories range from simple multiplication,
to the length of human pregnancy,
to the usual craziness that surrounds anything Maya related
But being a space nerd, I'll go with eight 32 day months per year.
Now throughout its orbit any moon will go to four distinct phases
New moon, first quarter, full moon, and last quarter and then back to new moon
Need a crash course on lunar phases? Check out Crash Course
It's hard to imagine culture not using these celestial events to subdivide their months into weeks
so that's why it's handy to have a month length divisible by 4
32 divided by 4 is 8
Thus, four 8-day weeks per month seems logical.
And boom! Lunar calendar done!
Eight 32 local day months per year divided into four eight-day weeks
with a local day being defined as 24.26957878 Earth hours long
and a leap day added every 20th month. Cool!
But let's get a little more speculative and talk multiple moons
Let's call this guy our primary and let's give it a companion. Pro-tip: To keep the maths relatively simple
and to give your system extra added realism and stability,
place this new moon in a first-order mean motion resonance with the primary moon.
Links on screen are in the doobly-doo for more on resonances but tldr,
all this means is that the inner moon should orbit x times for every y orbits of the outer moon
where x and y are whole numbers that differ by one
So like 2 is to 1, 3 is to 2, 4 is to 3, that kind of thing
I'll go with 3 is to 2,
meaning the inner moon will complete 3 orbits for every 2 orbits the outer moon completes.
Oh, and FYI, make sure to double-check with this video to ensure that this move is, in fact,
So three orbits of 32 local days is 96 local days, 96 divided by 2 is
48, so our outer moon's period, a.k.a. its month, will be 48 local days in length
As before, it will have 4 distinct phases
48 divided by 4 gives us four 12 day weeks
Now if 12 days seems like a bit too long a week length consider using the secondary intermediate phases of the moon:
Waxing crescent, waxing gibbous, waning gibbous, and waning crescent
to break that amount into eight six-day weeks
And let's all take a second to fully appreciate the mouthfeel of
So there you have it, two calendars
perhaps one culture on our planet will track the inner moon and maybe another will track the
outer moon or maybe a third culture will decide to track both moons at the same time
Like maybe that culture's year is marked by the outer moon say 10 orbits
and the month is marked by the inner moon
15 months say and maybe the phases of the inner moon mark the weeks
Perhaps significant religious events will occur during eclipses or when the moons share the same phase
FYI Here's some info on eclipses calculators.
Now, it's also worth considering when does a month begin,
which phase of the moon starts the month, and what are the cultural reasons for doing so
Earth-based lunar calendars often start their months on the new moon,
but if a culture had the whole one deity per month thing,
perhaps they might start their month on the full moon,
a shining heavenly light heralding the coming of a new deity. Anyways,
That's years months and weeks done. Next up hours minutes and seconds. As always,
I highly recommend taking this local day value and just have the locals on the planet call it
24 hours, 60 minutes, and 60 seconds.
Slightly redefining what these words mean can make it easier for audiences to consume our works.
But here's an interesting alternative scenario, stolen unabashedly from KSR's Mars Trilogy
Imagine our planet is a distant Earth colony
the colonists will notice that the day is super close to an Earth day
Instead of coming up with a new system of units and subdivisions of time,
they might just stick with their ingrained Earth
hours, minutes, and seconds and just hack off time at the end of day to compensate. Like all of this
accounts for about 16.18 Earth minutes
So we could have 24 normal Earth hours and at midnight say stop all the clocks and have
16.18 minutes of time slip before
continuing on with the regular 24 hours the next day. This could be a
period of ill omen a sort of witching hour a period where
inhibitions are shed or maybe just a period where one contemplates their next video on loony solar calendars
Good morning interweb! New plan
I am a fallible human, and I make mistakes sometimes
so in an effort to make sure we're all square and not to disseminate false information
I'm going to start correcting those mistakes in this section of the video.
So in the last video I misspelled "World Building"
like an idiot. I also wrote that a second is
1/60 of an hour it's not it's 1/60 of a minute, clearly so two small typos.
I'm really sorry. And the last point isn't so much a correction but more of a clarification.
A lot of people in the comments pointed out that I was wrong in saying that May
falls in Summer and this is correct if it comes with the caveat that May does not fall in summer
where I live because how many seasons there are what we call them
and when they happen is largely down to
where we live on the planet and how our culture deals with nomenclature. So growing up in Ireland,
I was always taught that summer is May, June, July
and this could be entirely different for you based on where you live
But the point of that section was to say that solar calendars fix dates and seasons
So whatever season may happen to fall in for you it will always fall in that season
year in year out because of the intrinsic properties of solar calendars.
So there you go. Two typos, one small clarification
And I'm really sorry for those little mistakes
They're really hard to eradicate
And I'm trying my best
Anyways, click the links on screen or in the description for more Artifexian content.
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Thank you all so much for watching!
Edgar out!