Thirteen month year

[Aldarion]

I had been doing some recalculation of my calendar, when it occured to me that it would be much simpler to simply have month roughly match up to lunar month. Synodic month is 29,5 days. But with 7-day week, one moth could be four weeks or 28 days. Now, with 29,5 day month, one year would have 12,37 months; with 28 day month, it would have almost exactly 13 months. But would that cause problems - there must be a reason why 12-month year is standard, possibly due to advantage of easy division into quarters? Also, I have already achieved a perennial calendar with a 12-month year, albeit through usage of intercalary days.

 

[Insolent Lad]

I gave one of my cultures the 13 month calendar—4 weeks of 7, 28 day month, with the extra day (2 on leap year) falling on the Yule not being counted as a day of the week. I think one reason for the 12 month calendar is because it works with the seasons. 13 months do not fit into a 4 season calendar very well. Season changes and the festival days associated with them play better with 12 months.

 

[MrNybble]

Assuming all this is based on a 365.25 day year? Not that I always to follow even the most basic of chronological rules as we know them. Could even adjust the hours to change the days so they fit into the months easier.

 

[Aldarion]

I gave one of my cultures the 13 month calendar—4 weeks of 7, 28 day month, with the extra day (2 on leap year) falling on the Yule not being counted as a day of the week. I think one reason for the 12 month calendar is because it works with the seasons. 13 months do not fit into a 4 season calendar very well. Season changes and the festival days associated with them play better with 12 months.

That was my thought as well. 13-month calendar may be more correct chronologically, but it wouldn't fit the seasons. Though I am thinking of having my world be basically in permanent spring or summer, but that too is something I haven't worked out that well... impact on fauna, culture - would advanced civilization even develop? - etc.

 

[skip.knox]

I'd start with the year. Make it 360 days or some other figure easily factored, but still fairly close to an Earth year. Then make months and weeks and seasons from that. So, 4 into 360 makes 90. Each season is 90 days. Three months into 90 days yields 30 days. That factors into three weeks of ten days each. You could work the arithmetic around in other ways, if you wished.

Or work in the other direction. Each day is comprised of ten hours. Ten days is a week, ten weeks a season. You could invent five seasons rather than four. Lots of room for improvisation!

 

[Aldarion]

I'd start with the year. Make it 360 days or some other figure easily factored, but still fairly close to an Earth year. Then make months and weeks and seasons from that. So, 4 into 360 makes 90. Each season is 90 days. Three months into 90 days yields 30 days. That factors into three weeks of ten days each. You could work the arithmetic around in other ways, if you wished.

Or work in the other direction. Each day is comprised of ten hours. Ten days is a week, ten weeks a season. You could invent five seasons rather than four. Lots of room for improvisation!

That would be possible in an artificially created world, but my world is (at this point anyway) supposed to be Earth in far future (let's say that technological development doesn't work out too well for us...)

 

[MrNybble]

All these days in a year thing, does it only apply to civilizations on the surface of a planet? What if they are deep underground. What about being in something that does not spin like a tidal locked planet? Possibly on a space station in deep space? No sun, orbit, or rotation does put a hamper on a calendar.

 

[Leonardo Pisano]

A day is linked to the spin of the earth, a weak has no such link, a month has to do with the moon cycle. The 365 days in a year are not 100% accurate, hence they adjust every four years, but not always. The correction every four years take place in February, because the Romans started the year in March (as you probably know), That's also reflected in September - December which come from 7-10 (septem is Latin for 7, etc). You could creat a counting system anyway you like. Why not simply use quarters, matching the seasons which are caused by the position towards the sun. So you are not 38, but 152 quarters (or seasons). The seasons it itself could be corrected for accuracy purposes, maybe by official announcement by your Earth Gov.
Of course I like 13 more than 12, as it is a Fibonacci number.
HTH.

 

[Saigonnus]

My world of Aern has 3 moons, and orbits it's sun every 400 days. I chose to have the year consist of 10 months of 40 days. It is further divided into "seasons"; which was originally based on the orbit of the furthest moon; which reaches full every 50 days, so every two full moons is a season. On top of that, a day on Aern is 30 hours long.

 

[Aldarion]

A day is linked to the spin of the earth, a weak has no such link, a month has to do with the moon cycle. The 365 days in a year are not 100% accurate, hence they adjust every four years, but not always. The correction every four years take place in February, because the Romans started the year in March (as you probably know), That's also reflected in September - December which come from 7-10 (septem is Latin for 7, etc). You could creat a counting system anyway you like. Why not simply use quarters, matching the seasons which are caused by the position towards the sun. So you are not 38, but 152 quarters (or seasons). The seasons it itself could be corrected for accuracy purposes, maybe by official announcement by your Earth Gov.
Of course I like 13 more than 12, as it is a Fibonacci number.
HTH.

Week is actually linked to moon's phases. Four phases (7 days each) and one month (28 days). But then months got lenghtened because year has 365 days and four seasons.

 

[Prince of Spires]

You could look at the Chinese calendar, which follows the moon cycle. They have both 12 and 13 month years to keep things synchronised and the start and end dates vary when compared to our calendar.

 

[Saigonnus]

Another option would be to not have months at all, and instead, just keep track of days.

And thus it was written on the 234th day of year 20, second age.

 

[Malik]

Why 28-day months? Seriously; anybody?

What are the odds another world is going to have the exact same orbital mechanics as us? The same lunar period? The same distance from the same sized sun?

Get on Starchitect or PlanetMaker and start building. It's FUN.

This whole thing we read in fantasy after fantasy about the MC being "fifteen years old."

Hey, great; WTF is a "year?"

As an example, my series is set on an Earthlike planet that's actually a moon orbiting a ringed gas giant. Every 104 days they cross behind the gas giant and go through a six-day total eclipse; this marks the end and start of each season. Four rotations around the gas giant line up with one rotation of the gas giant around the sun; a 440-day year and roughly a 30-hour day. You can tell the seasons by the angle of the gas giant's rings. They don't have months, just seasons.

Also, crops, tides, and even menstrual cycles are tied to the 104-day lunar period. Everything--tree rings, formations of the cones on the snails--ties into 104 days. Do some research on everything on Earth that's tied to 28-day cycles; it'll blow your mind.

This means they have a population shortage--women are fertile one third as often as they are on Earth--so sex has become basically a sport, with everyone trying to get pregnant as often as possible. There are worse hobbies. This has led to a sex-positive and gender-equal society; further, the shortage of hands means that women pitch in and do the same things the men do: soldiers, blacksmiths, horse trainers, generals, political leaders, heads of guilds. It's completely gender-agnostic. On top of that, people have to adjust the way they farm and what they eat, and how it's stored, because in their world, crops that take longer do better, and that 104-day winter is a real bitch. The timing gets tricky.

Breaking the 28-day cycle we use here on Earth made me throw out the entire rulebook and come up with a completely new set of circumstances to build around, which gave me a world that nobody else has, which IMO is one of the points of being a fantasy author. The orbital mechanics run far deeper, too: because the gas giant is almost always in the sky, they never see true darkness. The MC from Earth can read at night by the light of the rings, while the people on their world don't see as well at night as he does. They've also developed deep superstitions about darkness; the six-day period is when the monsters come out and the dead visit. In houses and castles there is always, always, a light on--a candle burning, a fireplace going. Always. When I built their conlang I used the same root for dead and dark. You don't die; you get extinguished. They're terrified of darkness.

A really fun part of the orbital period is when the hero, from Earth, finds out the woman he's falling for is only "17 winters" old; however, psychologically and biologically, she'd be in her mid-20's on Earth. She learns he's 28, which is their equivalent of being nearly 40 and by all rights he should be a grandfather. It takes some explaining and it's all very fun.

Anyway. Break out of Earth time. Your worldbuilding will be better for it.

 

[TheKillerBs]

The world is a messy place with a ~29.5-day synodic month and ~365.25 solar year with no real way of reconciliating them, which is why cultures tend to pick what is most relevant to them for agriculture and use that as the basis for reckoning time. Generally, the rule of thumb for months and years is that if the seasonal cycle is very important to a culture, it will reckon time by solar cycles, usually using a marker such as a solstice or equinox (or in our case, a completely arbitrary date that we keep generally in sync with the solar cycle by a complex series of corrective measures), and will generally use 12 months because that divides the seasons evenly. If you have very little seasonal variation, you'll probably reckon time by the moon instead and either not give a hoot about the solar cycle (like the Islamic calendar). For those in the middle, there's the lunisolar calendar (like the Chinese calendar or the Hebrew calendar), which really, everyone should use because it's clearly the best system.

The problem with the 28-day month, 13-month year calendar is that it keeps track of nothing. The moon's phases will go out of sync immediately to the point that the 9th month will start on the full moon, the four seasons don't divide evenly, and the solar year will also phase out of sync and after two decades the solstices and equinoxes will be nearly one month away from where they started so it's no use for agriculture.

Anyway. Break out of Earth time. Your worldbuilding will be better for it.

Or it'll annoy readers when they realise the person they thought was a teen is actually in their mid-20s.

 

[Aldarion]

Why 28-day months? Seriously; anybody?

What are the odds another world is going to have the exact same orbital mechanics as us? The same lunar period? The same distance from the same sized sun?

Get on Starchitect or PlanetMaker and start building. It's FUN.

This whole thing we read in fantasy after fantasy about the MC being "fifteen years old."

Hey, great; WTF is a "year?"

As an example, my series is set on an Earthlike planet that's actually a moon orbiting a ringed gas giant. Every 104 days they cross behind the gas giant and go through a six-day total eclipse; this marks the end and start of each season. Four rotations around the gas giant line up with one rotation of the gas giant around the sun; a 440-day year and roughly a 30-hour day. You can tell the seasons by the angle of the gas giant's rings. They don't have months, just seasons.

Also, crops, tides, and even menstrual cycles are tied to the 104-day lunar period. Everything--tree rings, formations of the cones on the snails--ties into 104 days. Do some research on everything on Earth that's tied to 28-day cycles; it'll blow your mind.

This means they have a population shortage--women are fertile one third as often as they are on Earth--so sex has become basically a sport, with everyone trying to get pregnant as often as possible. There are worse hobbies. This has led to a sex-positive and gender-equal society; further, the shortage of hands means that women pitch in and do the same things the men do: soldiers, blacksmiths, horse trainers, generals, political leaders, heads of guilds. It's completely gender-agnostic. On top of that, people have to adjust the way they farm and what they eat, and how it's stored, because in their world, crops that take longer do better, and that 104-day winter is a real bitch. The timing gets tricky.

Breaking the 28-day cycle we use here on Earth made me throw out the entire rulebook and come up with a completely new set of circumstances to build around, which gave me a world that nobody else has, which IMO is one of the points of being a fantasy author. The orbital mechanics run far deeper, too: because the gas giant is almost always in the sky, they never see true darkness. The MC from Earth can read at night by the light of the rings, while the people on their world don't see as well at night as he does. They've also developed deep superstitions about darkness; the six-day period is when the monsters come out and the dead visit. In houses and castles there is always, always, a light on--a candle burning, a fireplace going. Always. When I built their conlang I used the same root for dead and dark. You don't die; you get extinguished. They're terrified of darkness.

A really fun part of the orbital period is when the hero, from Earth, finds out the woman he's falling for is only "17 winters" old; however, psychologically and biologically, she'd be in her mid-20's on Earth. She learns he's 28, which is their equivalent of being nearly 40 and by all rights he should be a grandfather. It takes some explaining and it's all very fun.

Anyway. Break out of Earth time. Your worldbuilding will be better for it.

As I have already pointed out to @slip.knox, my world is Earth of the far future, with civilization again going through Stone Age after a global catastrophe event similar to Toba catastrophe bottleneck, except on a global scale. So yes, the world does have same orbital mechanics, lunar period, same distance from same sized sun... because it is the same world. I mean, chances of humans evolving on another world are even worse another world having exact same characteristics as Earth. Of course, considering that we are talking civilizational regression here, I could have well have had humans settle all over the galaxy... but what could have caused galaxy-wide technological regression without wiping out humanity as such?

 

[Insolent Lad]

I decided early on that my primary fantasy world would have a similar set up, time-wise, as ours. It simplified matters and it is sort of 'next door.' That is, it is linked to ours by gates and in other subtle ways, of which I have only hinted (but have my theories!) I do raise the question once or twice as to whether it might be a slightly different sized world, whether length of day might vary a tad, etc. but I've gone on the assumption that it is 'close enough.' So I use the 365 day year and so on.

On the other hand, the worlds of the gods, although they have quite different dynamics going on, sort of synchronize themselves to the primary world as long as the gods travel back and forth occasionally. Otherwise, they would possibly drift apart and time flow at different rates. This does not mean they have the same length year, month, or anything else. Not that the gods care about time anyway, being immortal and all that.