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Calendars for dummies

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Calendars for dummies
Post by Imaginos1892   » Wed Apr 27, 2016 8:42 pm

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WHY O WHY would the Sharonans and Arcanans both independently invent calendars that incorporate exactly the same stupidities as the Gregorian calendar we're used to?

Start with the basics. A calendar has to keep track of 365 days in most years, 366 days in 97 out of every 400 years.

Would they have 7-day weeks, or weeks at all?

If you are going to have months, there are a bit over 13 lunar months in a year.

12 is a handy number, but why make one weird short month? 7 30-day months and 5 31-day months make a lot more sense, with one day added to a 30-day month for leap years.
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Don't open that!! It's the original can of worms!
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Re: Calendars for dummies
Post by phillies   » Wed Apr 27, 2016 10:34 pm

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Imaginos1892 wrote:WHY O WHY would the Sharonans and Arcanans both independently invent calendars that incorporate exactly the same stupidities as the Gregorian calendar we're used to?

Start with the basics. A calendar has to keep track of 365 days in most years, 366 days in 97 out of every 400 years.

Would they have 7-day weeks, or weeks at all?

If you are going to have months, there are a bit over 13 lunar months in a year.

12 is a handy number, but why make one weird short month? 7 30-day months and 5 31-day months make a lot more sense, with one day added to a 30-day month for leap years.
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Don't open that!! It's the original can of worms!


We may consider the ancient culture whose calendar included (but did not stop there) with 18 months of 20 days for a total of 100 days in that repeating cycle. (As the locals had invented the zero, they would have written 100 as indicated.) (their counting system was creative.)
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Re: Calendars for dummies
Post by Jonathan_S   » Wed Apr 27, 2016 10:37 pm

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Imaginos1892 wrote:WHY O WHY would the Sharonans and Arcanans both independently invent calendars that incorporate exactly the same stupidities as the Gregorian calendar we're used to?

Start with the basics. A calendar has to keep track of 365 days in most years, 366 days in 97 out of every 400 years.

Would they have 7-day weeks, or weeks at all?

If you are going to have months, there are a bit over 13 lunar months in a year.

12 is a handy number, but why make one weird short month? 7 30-day months and 5 31-day months make a lot more sense, with one day added to a 30-day month for leap years.
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Don't open that!! It's the original can of worms!
A month of around 30-ish days makes sense given that that's roughly a lunar month. And a lunar month is kind of obvious measure of time. Split that into quarters and you're at basically a 7 day quarter-month...
But why quarters instead of fifths? You could have a 5 6-days weeks in a 30 day month. And they even fit into the year about the same 52 7-day weeks comes up a day short 364 days) while 61 6-day weeks is a day long (366 days)

To some extent it probably matters what your society comes to think is a reasonable work to rest ratio is 1 in 7 (later 2 in 7) or 1 in 6.
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Re: Calendars for dummies
Post by Howard T. Map-addict   » Thu Apr 28, 2016 4:40 pm

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Actually a bit *under* 13 lunar months in a year.
The Jewish "lunar/solar" calender adds 7 "thirteenth" months
in each 19-year cycle.

HTM

Imaginos1892 wrote:{snip - htm}
If you are going to have months,
there are a bit over 13 lunar months in a year.

{snip}
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Don't open that!! It's the original can of worms!
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Re: Calendars for dummies
Post by thanatos   » Wed Jun 01, 2016 2:54 pm

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OK people, as someone whose had to explain this to quite a few religious cousins who insisted the Jewish calendar was more "precise" than the Gregorian calendar, here is some of the essential details on how and why both calendars came into being. First the Jewish calendar:

Originally (if the bible is to be believed) the ancient Hebrews used the egyptian calendar which was based upon the solar calendar for obvious reasons (mainly that the Nile overflowed at certain times of the years which needed to be known for agriculture). After the exile to Babylon, they adopted certain elements of the lunar calendar practiced in Babylon (including the names of the months). Yet there was always a specific edict to celebrate the Passover holiday in spring and as such the eldars would go into the fields and examine what stage the wheat was at. If it had not ripened sufficiently it meant that they were behind in the seasons and needed to add an extra month. It was only in 12th century I believed that Maimonides developed the mathematics needed to codify the process.

So a single lunar rotation is about 29.5 days (really 28.5 but an extra day is added by the earth's rotation) and thus the Jewish calendar has 6 month of 29 days and 6 months of 30 days - a total of 354 days. That means that every year the calendar slips back some 11-12 days relative to the solar (Gregorian) calendar. Maimonides calculated that in 19 years you would lose 209 days plus another 4 or 5 (depending on how many leap years happened to occur in the Gregorian calendar). So a total of 7 extra 30-day months needed to be added during this 19 year period plus 3-4 additional days. The added month is the gross correction of the calendar while the single day added (or sometimes subtracted in certain years) was a fine correction, that also served to ensure that certain holidays did not fall on certain days of the week (like Yom Kippur on a Friday or Sunday).

Now the Gregorian Calendar was created as a correction to the previous Julian Calendar, which had added too many leap years (because they didn't know that the earth's annual rotation took 365 days, 5 hours, 48 minutes and 46 seconds - not 365.25 days exactly). But originally, the Julian calendar had six 31-day months, Five 30-day months and one 29- or 30-day month (February, obviously). When Augustus Caesar decided that he wanted a month named after himself, he chose the month after July (which was name for Julius Caesar, who'd instituted the new calendar). But not wanting to seem less than Julius Caesar, he ordered an additional day be "stolen" from February and added to his month (August), which is why it has 31 days. The original Roman calendar only had ten months - which is why the last four months translate to "seventh time" (September), "Eighth time" (October), "ninth time" (November) and "tenth time" (December). I think 12 months was more workable and better aligned with the lunar cycle, which is more important to herders who need to calculate the birth cycles of their sheep and cattle (not sure on this though).

So having Arcana and Sharona have 12 month calendars makes sense if the basic parameters are the same (i.e. same length of days, lunar cycles and solar cycles). When the years start though and the names and lengths of the months would be different, but other parameters would still be the same.
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Re: Calendars for dummies
Post by tonyz   » Thu Jun 02, 2016 11:27 am

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Given that these are alternate Earths with lots of things the same, we can probably assume that Earth's orbital length, the Moon's period, etc., are exactly the same in all the universes.

But we don't seem to have any evidence as to whether these civilizations use solar (365.24 days/year like the Gregorian calendar), lunar (pure lunar months like the Islamic calendar, NOT adjusted with intercalary months), or lunisolar (lunar months but additional months added periodically to keep in track with the seasons/sun) calendars. It's even possible that either civilization could have yet other types of calendars! Or that the three Arcananan civilizations have different calendars. We probably won't get any evidence unless it becomes a plot point somewhere.

(runslikecelery probably has details -- but compare the Manticoran calendar infodump in one of the earlier Honor books, which has never since been a plot points of any interest as everyone just uses T-years for everything -- so why take up space telling us things like that when the author might get a Better Idea later?)

Weeks are probably the most likely to not be around, at least in the seven-day form. True, that's about a quarter of a month, but it rapidly loses contact with the rest of the cycle. Civilizations on Earth have generally found some period of time shorter than the month to be convenient, but there have been quite a few different periods used (not to mention things like, say, the Mayan calendar round....)
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Re: Calendars for dummies
Post by phillies   » Tue Jun 07, 2016 2:39 pm

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The notion that months are lunar corresponds to an oddity of the English language; in most languages the words for month and Luna are quite different.

There is a plausible reconstruction of the original innovation of the zodiac, leading to twelve constellations with particular features, which explains why there are 12 months, namely four quarters of the year, and two resets due to precession of the equinox. One can even estimate the date at which the first four constellations were inserted into the zodiac.
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Re: Calendars for dummies
Post by tonyz   » Tue Jun 07, 2016 2:57 pm

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phillies wrote:The notion that months are lunar corresponds to an oddity of the English language; in most languages the words for month and Luna are quite different.

There is a plausible reconstruction of the original innovation of the zodiac, leading to twelve constellations with particular features, which explains why there are 12 months, namely four quarters of the year, and two resets due to precession of the equinox. One can even estimate the date at which the first four constellations were inserted into the zodiac.


One strongly suspects that lunar months long predated the zodiac (among other things, the moon is a LOT more obvious and a LOT more useful for people doing anything at night). You need a lot of observation to note things like equinoxes, precession, etc.
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Re: Calendars for dummies
Post by phillies   » Tue Jun 07, 2016 3:48 pm

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tonyz wrote:
phillies wrote:The notion that months are lunar corresponds to an oddity of the English language; in most languages the words for month and Luna are quite different.

There is a plausible reconstruction of the original innovation of the zodiac, leading to twelve constellations with particular features, which explains why there are 12 months, namely four quarters of the year, and two resets due to precession of the equinox. One can even estimate the date at which the first four constellations were inserted into the zodiac.


One strongly suspects that lunar months long predated the zodiac (among other things, the moon is a LOT more obvious and a LOT more useful for people doing anything at night). You need a lot of observation to note things like equinoxes, precession, etc.


However, the zodiac predicts the *seasons* which is vastly more useful for anyone doing agriculture, which is why we can estimate the origin of the zodiac at 12 or 16 thousand BC. With fire for light, people are not doign things at night.

However, there is a published claim based on scratches on bone of an effort to measure the length of the month, dating to ca. 40,000 BC.
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Re: Calendars for dummies
Post by Terranovan   » Mon Jul 18, 2016 1:05 am

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According to my best memory of the appendix to RTH, one of the calendars has an error in arithmetic. Specifically, it has 366 days in its year, and 367 for a leap year. Conceded:
It's been so long since I read the book that I don't even remember which one of the calendars is off.
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