timekeeping and calendars

[Emily]

curious to hear about people's calendars and timekeeping

in the modern gothic descendant i'm working on, they keep time basically the same way we do, but i had to put a lot of thought into the names of the months

in a different conworld i'm working on, that's roughly earth-sized but has two moons, i am struggling to figure out the math behind what the sky would look like at any given time on any given day; once i do, the next step is to figure out how this works into a calendar—the month in most earth calendars is based on the lunar cycle of ~29 days, but the concept of a month would be very different in a world where there was a second moon whose cycle was half the length of the other

also, i'm curious (especially for those whose conworlds/cultures are approximately at the same stage of technological and/or social development as present-day earth) whether your cultures have time zones, how they divide the day into workable units, and how much this is or isn't standardized across the world. (one early conlang i did, set in europe in the first millennium CE, tracked their time with sundials, which meant an "hour" would be variable lengths depending on the length of the day)

[Man in Space]

I made a post about this in the Twin Aster topic, if you’d like to check it out.

[evmdbm]

I have a moon, but I ignored it... made it just big enough to have tides and then paid no attention in calendars. That was simply because I found a formula - somewhere, can't remember where now - for working out the length of days and years. It turned out there were going to be 352.05 days in the year, which made 35 weeks of 10 days (plus midsummer and midwinter and a leap year every twenty years the obvious solution.

Time zones... now there's something to work out.

[Raphael]

I have a moon, but I ignored it...

That would make a great opening line for a novel or story.

Also, now I wonder what people not familiar with conworlding would make of that statement...




(Myself, I'm still completely undecided on how to subdivide the year in my conworld.)

[Richard W]

If the moons are in resonance, there would still be a lunar cycle, but just more complicated than ours. If the brighter moon were the one with the shorter period, then I would expect it to be that one that dominated the counting, with two different types of month.

[masako]

mine is here

[Ares Land]

The Simbri word tarande means both 'calendar' and 'civilization'; it's also used for a geographic area, and all people who inhabit it (the Tarandim.)

I'll be counting in local days throughout (in our terms, they are 25 hours, 21 minutes long)

The year (Simbri in, pl. inda) is 333.8 days (ya, pl. yachi). More on this later.

The lunar year.

Massotis has two moons: Yebon (period: 16.162 days) and Mosin (period: 24.244) -- the two are in orbital resonance.

2 periods of Yebon, or three periods of Mosin make up a matlat, pl. matlit).

There are seven matlit in a lunar year: Komer, Moma, Xaxxan, Beni, Yer, Aron and Nenom.

A matlat is, alternatively, 48 or 49 days, so the lunar year (tlonin, pl. tloninda) is, alternatively 339 or 340 days long.

The Tarandim make no attempt to adjust the lunar year to the solar year. The current year is in 5028, tlonin 4944. To be more specific -- the Tarandim count in base twelve -- it is in 2ab0, tlonin 2a40 -- and in fact, almost always given as b0, 40.

The matlat is divided into 12 'weeks' of four days. The days of this week are qoo, 'root', lis 'leaf', soya 'flower', yachô 'fruit'.
When the matlat is 49 days long,the extra days is called tlanda

The solar year.

The solar years is divided into 6 seasons.
The new year (in tabarsis) isn't counted as part of a seasons; it's immediately followed by batcha (late summer), 56 days, followed by nonda 'autumn' (55 days), nankot 'winter' (56 or 55), qatcha 'early spring' (55), nacha 'spring' (56) and morat, 'summer' (55)

One year out of five, winter has only 55 days.

It is again, traditional, to give the date in both lunar and solar calendar; 3b Nankot, 29 Xaxxan, qoo ('47 winter, 33 Xaxxan, Root day').

Days of rest

Add to this a second lunar reckoning, this time based on the draconian periods. Days of rest (tawcha, pl. tawchi) occur when one of the moons occurs at perigee, at apogee or at the lunar nodes. This occurs at least every four days.
(The reckoning is complex, but the periods considered are a day or so shorter than the lunar periods considered above.)

There are religions obligations associated to root, leaf, flower or fruit days, and of course to tawchi.
Other than that, religious holidays (of which there are too many to describe here) are also tawchi.

The main taboo is that agricultural work should be reduced at a minimum on a tawcha. By extention, any labor of importance should be avoided.

[Emily]

another calendar question: astronomically an equinox is apparently when the sun crosses the equator, so lists of equinoxes have exact times of day, which of course are rendered as different times in different time zones, and can be at any real time of day including the middle of the night. this is all well and good for the astronomer, but the cultural (and, in pre-heliocentric reckonings, the only or at least primary) understanding of an equinox is when day and night are (almost) equal lengths—so a period of 12 or 24 hours, rather than an exact instant. my question is, how do i "convert" from the former definition to the latter? if a given year's vernal equinox takes place at 9:52 pm on march 20 in location xyz, does that location's observed equinox take place on the 20th or 21st?

[Torco]

depending on tech level, this may be an unanswerable question: whichever day duration is closest to exact 12 hours, as far can be measured, would be considered the equinox and that's it, I'd think.

[mocha]

Until recently I was basing the perceived year length of my conworld off the sidereal year, naively assuming axial precession would be negligible. But then recently it occurred to me that since its major moon is much closer than our moon, I should actually figure out how to calculate the actual precession period. Well, turns out, it would make a full precession cycle in about 320 Earth years (instead of ~25000 years like our Earth).

This translates to a tropical year 1h36m shorter than a sidereal year, so I had to slightly tweak leap year rules. And as a corollary I think it may now be unreasonable to assume cultures on the world develop a concept of "pole star", considering how fast it would change over even a single lifetime.

For some additional context, this is a roughly Earthlike planet orbiting a somewhat smaller star, mutually tidally locked to a moon slightly larger but much closer to the planet. Therefore, since a "month" would just be a day, the primary subdivision of a year would be the season, which with its orbital period ends up being pretty close to the length of a normal Earth month.

Full time unit conversion:

~Day = 28 Earth Hours
~Week = 6 ~Days, which translates to about 7 Earth Days
~Season = 4 ~Weeks, which translates to about 1 Earth Month
~Year = 3 ~Seasons
"Bikêm" = 20 ~Years (or about 4 Earth Years)

The lore goes that the Bikêm came about as astrologers based important ceremonies, holidays, and rites on the cycle of the planet Bikê, and since its synodic period is about 20 local years this got translated in common parlance to a period of exactly 20 local years. I have been basing cultural age terminology off this since it feels to be a more reasonable unit than a period of 3 months...

[Torco]

Ellirnae (something like [e'ʝɨɾ.nə], I suppose), my current conworld, is a mars-sized moon orbiting a superjupiter called Tarka. Another of its peculiarities is that the difference between its rotational inclination, its orbital inclination and its jupiter's orbit around the local star are so small that it, for all intents and purposes, has no seasons. It's day lasts a bit over 40 hours, 20 night 20 day, and the whole tarka-ellirne system takes ~160 local days to complete a year. By a cosmic coincidence, this comes out to almost exactly the amount of time a human pregnancy takes to completion.

Because of the lack of seasons, the people of ellirnae aren't as interested in calendars as humans in worlds with seasons, such as Earth. while many ellirnean societies are agricultural, the relevant information for a farmer is more related to when the next rains will come, which is something calendars don't help with. Nevertheless, measuring time is still a useful thing to be able to do: I haven't come up with actual calendars, but I'm thinking something more along the lines of periods upon periods: "months" and "years" that don't necessarily add up to a proper orbital year, since the orbital year is not very releant, but rather that just make for useful durations in order to talk about, say, how much time I will loan you my cart or whatever.

[Moose-tache]

Not enough conworld calendars incorporate the Metonic cycle.

Every 19 years, the lunar cycles return to the same position within the solar year. By the time this happens, the lunar calendar is exactly seven phases behind, so you can add a month to seven of the nineteen years as scheduled leap months. This allows the months to still follow the actual phases of the moon, and occur in roughly the same time of the year, with an error of only about an hour per decade. We imagine ancient Chinese, Romans, and Greeks adding intercalary months based on ad-hoc direct observations, but most of the time they were just following the Metonic cycle.

[foxcatdog]

Metonic cycle?
Lack of true Solar Eclipses?
Leap Years?
Other astronomical gibberish like star cycles or whatever they are called?
All boring which is why i made the Bindgingverse have none of that handwaved of course by being a constantly expanding magic orb. A year is a year with perfectly aligned seasons, days and lunar cycles all caused by the magic system.

[keenir]

Other astronomical gibberish like star cycles or whatever they are called?

You could always use sunspots...a ten-year cycle, and they also recently may have found evidence that Sol also uses a 17-year cycle.

All boring which is why i made the Bindgingverse have none of that handwaved of course by being a constantly expanding magic orb. A year is a year with perfectly aligned seasons, days and lunar cycles all caused by the magic system.

Um...maybe we're using the word boring differently, but doesn't that word mean that nothing happens?

[foxcatdog]

I'm sure some people find calculating how the solar/lunar metaphonic cycle affects the breakup of the world's supercontinent but for me its the most tedious inanity much better spent on doing something else.

[sangi39]

Not enough conworld calendars incorporate the Metonic cycle.

Every 19 years, the lunar cycles return to the same position within the solar year. By the time this happens, the lunar calendar is exactly seven phases behind, so you can add a month to seven of the nineteen years as scheduled leap months. This allows the months to still follow the actual phases of the moon, and occur in roughly the same time of the year, with an error of only about an hour per decade. We imagine ancient Chinese, Romans, and Greeks adding intercalary months based on ad-hoc direct observations, but most of the time they were just following the Metonic cycle.

I did for what I intended to use as a calendar for my moon druid in D&D. Then I asked out DM how long the year was in our campaign and he said "300 days"... completely messed up my plan. Still keeping it, because, hey, I enjoyed making it



"H" indicates a 29 day month, "F" a 30 day month, and they more or less alternate one after the other. Intercalery months are added in at regular intervals, and every so often the fifth month in a year, which is usually short, is long instead (marked with a red "F"). So you have years that are 354, 355, 384, and 385 days long

[Raphael]

I did for what I intended to use as a calendar for my moon druid in D&D. Then I asked out DM how long the year was in our campaign and he said "300 days"... completely messed up my plan.

Ouch! Sorry to hear that. Neat concept, though!

[sangi39]

I did for what I intended to use as a calendar for my moon druid in D&D. Then I asked out DM how long the year was in our campaign and he said "300 days"... completely messed up my plan.

Ouch! Sorry to hear that. Neat concept, though!

Haha, it's fine. I was hoping that I'd be able to use it to kind of go "oop, it's the Day of the Waning Quarter, I've got to go do this quickly" just to add a bit more flavour to the character, add in a bit of conflict between swamp/forest-dwelling borderline hermit and having to go out into the wider world

I've more or less decided that any time I make a new character, though, they get a new calendar. We started playing Drakkenheim recently, so new character, new calendar, and this character uses one that, similar to the Bahá'i calendar, has 19 months of 19 days each, for a 361 day year, but it doesn't add in the extra four/five days to make up the difference, meaning it's an incomplete solar calendar. And they also use a lunar calendar of 354 days (12 months alternating between 29 and 30 days each) alongside that. Similar to the Mayan calendar and the like, this gives each day a unique date for about 350 solar-years (coincidentally about the lifespan of a dwarf, which my character is, so that worked out nicely). There's also a 5-day week that works alongside that, which then gives each day a unique date for 1750 solar-years (if you need to refer to a specific 354-day-year, you refer to the date in the 19x19 cycle that the lunar new year fell on)

[mocha]

Not enough conworld calendars incorporate the Metonic cycle.

Every 19 years, the lunar cycles return to the same position within the solar year. By the time this happens, the lunar calendar is exactly seven phases behind, so you can add a month to seven of the nineteen years as scheduled leap months. This allows the months to still follow the actual phases of the moon, and occur in roughly the same time of the year, with an error of only about an hour per decade. We imagine ancient Chinese, Romans, and Greeks adding intercalary months based on ad-hoc direct observations, but most of the time they were just following the Metonic cycle.

I did for what I intended to use as a calendar for my moon druid in D&D. Then I asked out DM how long the year was in our campaign and he said "300 days"... completely messed up my plan. Still keeping it, because, hey, I enjoyed making it

(image)

"H" indicates a 29 day month, "F" a 30 day month, and they more or less alternate one after the other. Intercalery months are added in at regular intervals, and every so often the fifth month in a year, which is usually short, is long instead (marked with a red "F"). So you have years that are 354, 355, 384, and 385 days long

A while ago I devised something conceptually similar. According to my notes:

• Normal years have twelve months of 29 or 30 days.
• Even-indexed months (starting with 0) have 30 days, while odd-indexed months have 29.
• If the year mod 19 mod 4 is 0, the second month (index 1) has a leap day, totalling 30 days instead of 29.
• If the year mod 19 mod 3 is 0, there is a leap month at the end of the year.

Although this was more just a tangent and I certainly didn't put as much effort into an aesthetic table like that!

[mocha]

Metonic cycle?
Lack of true Solar Eclipses?
Leap Years?
Other astronomical gibberish like star cycles or whatever they are called?
All boring which is why i made the Bindgingverse have none of that handwaved of course by being a constantly expanding magic orb. A year is a year with perfectly aligned seasons, days and lunar cycles all caused by the magic system.

90% of the reason I developed my astronomy utility was to do calculations on my conworlds to make sure everything adds up. It has been a truly insane amount of effort for something, quite frankly, no one cares about, but I enjoy having that level of detail nonetheless.

Alternatively, I can also take comfort in that no one will be able to point out silly JK Rowling-esque math errors in my projects.