Talk:Lunar calendar

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—Yamara ✉ 22:07, 12 February 2008 (UTC)
thread_title:  [[Wikipedia:WikiProject_Time/Assessment|WikiProject Time assessment rating]] comment 

message: Question: If the Islamic calander can not be used to determine season then how do farmers sow the seeds in different Islamic countries.
Today I can understand they can use the Gregorian calendar because both are available, but how was the situation a centuries back? 
Any idea?
::In Egypt, the Egyptian (Coptic) solar calendar never stopped to be used by farmers, including muslim farmers. In the Middle, East both the Hebrew lunisolar calendar (derived from the Babilonian calendar) and the Julian solar calendar (derived from a mix up old the Roman lunisolar calendar and the Egyptian solar calendar) have alwasy been in commonin use beside the Islamic lunar calendar. Curiously, some Arab country traditionally use the Hebrew month names for naming the corresponding Julian months. 194.176.201.27 (talk) 11:39, 23 May 2008 (UTC)
thread_title: Discussion

message: Are there any examples of a purely lunar calendar besides the Islamic calendar?  The article would be greatly improved if we had some.  If other examples don't exist, I'm not quite sure what the purpose of this article would be.--Pharos 18:28, 21 October 2007 (UTC)
replies: text: At least another example exist: the so-called "Lunar series" used in the Mayan calendrical system. That was a special-purpose calendar (possibly used to calculate lunar ellipses) composed of *six* lunar months. Adding this example would also be good to make the point that, in a lunar calendar, what really matters is the month length, while the "year" is just an arbitrary number of months collected together. This is opposed to the solar calendar, where what really matters is the duration of the year, and "months" are just arbitrary internal subdivision of the year (in fact, there are solar calendards with 19 19-days months, or 18 20-days months, but they all result in 365 and a quarted days per year). 194.176.201.24 (talk) 11:27, 23 May 2008 (UTC)
thread_title:  Non-Islamic use? 

message: The section titled "Old English 13-month *lunar* year" does not make sense, because that calendar acually was *not* a lunar, calendar but rather a *solar* calendar with an anusual internal subdivision (13 four-week periods plus 1 day, totalling *365* days!). And, once you have corrected the error and turned it to "Old English 13-month *solar* year", it doesn't belong in this article anymore... So, if everybody agrees (or I have no answers within a few days), I will correct that "lunar" intto "solar" and move the whole section in the "Solar calendar" article. 194.176.201.24 (talk) 11:29, 23 May 2008 (UTC)
replies: text: The only reason for not moving it would be if it was ever called a lunar year or its months called lunar months in the historical record, rightly or wrongly. However, the present section does not support that possibility. — Joe Kress (talk) 21:02, 24 May 2008 (UTC)
replies: text: Even if that was the case, in this article it would suffice to leave just a short note about the weird denomination, with a link to the proper article. 151.47.164.116 (talk) 12:41, 26 May 2008 (UTC)
thread_title:  "Old English 13-month lunar year" section 

message: This is a good, informative article, but I think the "Length of the Lunar Month" section needs a little more clarification. I spent a good five minutes trying to figure out what exactly those numbers were supposed to mean, and how one could "use" them, and couldn't figure the latter out at all. My mother couldn't make heads or tails of it, either. We normal people need a little more explanation, please! 70.212.131.245 (talk) 20:20, 26 May 2008 (UTC)
thread_title:  Clarification 

message: I removed the Dreamspell Calendar stuff, It is from a cranky non-notable site and not even a lunar calendar. It belongs in Calendar Reform if anywhere. Megalophias (talk) 00:59, 26 February 2009 (UTC)
thread_title: Dreamspell Calendar

message: Deleted "It takes this long to complete a single revolution round the earth" from the "Length of the lunar month" section. The *sidereal* month is the time it takes the moon to complete a revolution around the earth (27.322 days); the *synodic* month is longer. A good explanation of this can be found at http://www.sumanasinc.com/webcontent/animations/content/sidereal.html .  —Preceding unsigned comment added by Eggsyntax (talk • contribs) 22:27, 22 June 2009 (UTC)
thread_title:  Deleted erroneous statement about the synodic month. 

message: There is a link to a lunar calendar.  It goes to a page that is selling a lunar calendar.  For what it is worth, it is a beautiful calendar, but I don't see any other info on that page that contributes to this topic.  — Preceding unsigned comment added by Hubie (talk • contribs) 18:28, 3 February 2011 (UTC)
replies: text: Removed it and another because they discuss lunar phases, rather than lunar calendars. — Joe Kress (talk) 06:40, 4 February 2011 (UTC)
thread_title:  Dmtr external link

message: Aww no fair, there is nothing on the Inuit's lunar calendar? felinoel (talk) 17:18, 17 April 2013 (UTC)
thread_title: Inuit Lunar Calender

message: I note the partial reversion of my change wherein I had amended some of  the "1 day off after X" figures; the explanatory note says "the exact amount depends on change of the synodic month value."
I appreciate that "round numbers" make for simpler explanations, but surely the main point of using rational number with small denominators as estimates for the synodic period is to enable simple calculations, and thus it is important for one to know when one must stop using such calculations. Accordingly the time limits should be rounded down rather than up. (To be fair, depending on time of day, one can be "out by a day" well before the limits given; perhaps that needs explanation too.)
Most synodic variation is not due to stochastic processes (where random variations may accumulate); on the contrary, most synodic variation is cyclic, primarily due to earth-sun orbital eccentricity (which mostly cancels out every year, and completely cancels out every 19 years) and moon-earth orbital eccentricity (which cancels out every 15 anomalistic months). The non-cyclic change over 70 years is about plus 13 milliseconds. See Lunar Periods.
Perhaps there is some other reason I have missed, but  "change of the synodic month value" on its own does not seem like sufficient reason to assert that "off by one day after about 70 years" is a better error-limit than "off by one day after about 68 years".
Martin Kealey (talk) 13:03, 27 April 2013 (UTC)
thread_title:  Using rounded numbers for error limits 

message: The calendar type selection in the upper right at the beginning of the article points to many calendars, including Gregorian and plenty Islamic calendars... yet strikingly, even this being lunar calendar article - the table is missing the link to Chinese calendar.  — Preceding unsigned comment added by 79.233.82.242 (talk) 10:27, 9 March 2016 (UTC)
thread_title:  Calendar table in the upper right 

message: Substituted at 22:37, 29 April 2016 (UTC)
thread_title: Assessment comment

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thread_title:  External links modified 

message: I haven't made up my mind whether I think that that table in the section "Length of the lunar month" needs A) more work, or B) to go.  It is somewhat informative, after one does a lot of thinking about what it actually says.  It's sort of explained (if one doesn't obsess over "Continued fractions") in the text, although it could be clearer.  The fractions presented come successively closer to the actual length, in days, of the synodic month.  So one sets up some sort of cycle: one takes the number of days given in the numerator, and divides it into the number of months given in the denominator (devising some sequence of 30-day and 29-day months).  And then after the time given, your calendar will be about one day off of the actual moon month.Two other pieces of information might be worth presenting in the table:
* How many 30-day months and how many 29-day months does it need to make up each cycle (I've done some figuring, and it seems there's one correct answer in each case);
* Which way is your calendar a day off after the length of time, i.e., is your calendar running one day ahead of the actual moon month, or one day behind it.
Both of these can be worked out fairly easily with some basic high school algebra.  And I'm thinking I could do that and make the table more informative/complicated.  But I wonder if that would amount to original research.  On the other hand, I wonder if someone did just that sort of work to devise the table to begin with. Uporządnicki (talk) 17:44, 20 May 2020 (UTC)
replies: text: I forgot to say, I'm hoping for people's comments.  I'm kind of itching to expand that table, but I don't want to do a whole lot of work and have it validly removed.  Uporządnicki (talk) 11:24, 21 May 2020 (UTC)
thread_title:  Table at "Length of the lunar month" revisited 

message: About that point just added in a new "popular culture" section--I'm inclined to think that its relevance to the article is kind of a stretch, and its interest and appropriateness is kind of marginal.  Thoughts? Uporządnicki (talk) 17:46, 28 May 2020 (UTC)
replies: text: Agreed. I am going to remove it for now, if anyone strongly disagrees with the removal they can go ahead and revert me. Greyjoy talk 05:11, 22 August 2020 (UTC)
thread_title:  That "popular culture" point 

message: I just discovered that I made a major blunder in that table I expanded--the one about the 29- and 30-day months.  When I said that this or that distribution would have the calendar a day ahead of, or behind the moon phases, it seems I had them exactly reversed.  To illustrate, if you start on the full moon and make all your months 29 days long, after two months your calendar will show a new month about a day BEFORE the full moon.  That is to say, your calendar will be AHEAD of the moon phases--not behind, as I had said.  On the other hand, if you make all your months 30 days, then after two months the calendar will show a new month about a day AFTER the full moon; the calendar will be one day BEHIND the moon phases--not ahead, as I had said.
I think it was a language glitch in my head, not a math one.  At some point, when I have more time, I'll go through the others in the table, redo the arithmetic, and double check that I have them all the right way round as far as "ahead of" and "behind." Uporządnicki (talk) 13:33, 3 October 2020 (UTC)
thread_title:  Fixed big error I made in that table I so lovingly edited 

message: All the calendars in the current version of this "lunar calendar" article are based on the phases of the moon (the synodic month of about 29.5 days, with about 12.37 synodic months per year).
Some sources mention a "lunar-stellar calendar",
where each month begins when the moon passes the Pleiades (a sidereal month of about 27.3 days, with about 13.37 sidereal months per year),
without regard for the moon phases.
Kaldarkhan Aliseituly Kambar.
"New Look at the Modern Codification of the Mayan Calendar".
In other words, the day of the month in lunar-stellar calendars corresponds to the lunar station.
Should this article say a few words about such "lunar-stellar calendars",
or is there some other more appropriate article about such calendars?
--DavidCary (talk) 23:03, 6 October 2020 (UTC)
thread_title:  lunar-stellar calendar 

message: Native american tribes have used a turtle’s back pattern of scales to establish the lunar calendar cycle. The peripheral scales surrounding the edge add up to 28, the number of days of a lunar cycle.  The center of the shell comprises thirteen larger scales which represent the 13 moons of a year.
I've removed this section, as the veracity of these claims, in particular that "the center of the shell comprises thirteen larger scales which represent the 13 moons of a year" are extremely dubious. Although this section is cited, neither of these sources take into account that the lunar synodic month actually consists of 29.53 days, meaning this alleged lunar calendar fails to actually measure any lunar cycle with any accuracy, and that such a calendar of 13 months of 28 days actually more closely approximates the solar tropical year. So either the indigenous peoples who allegedly used this calendar completely failed in their purpose to measure lunar months, and somehow failed to observe the monthly shift between months and the lunar cycle, or these sources were unintentionally influenced by revisionists who were influenced in turn by Robert Graves (note that his "Celtic Tree Calendar", which also fails to be attested in the historical record and is widely used in neopagan and New Age circles, is also composed of 13 months of 28 days). The apparent total lack of any actual academic sources that can back up this "tortoise shell calendar" makes me suspect the latter is more likely. Midnight-Blue766 (talk) 20:26, 29 October 2020 (UTC)
thread_title:  "In First Nations culture" 

message: , I'm also hoping that the IP user whose edits you just reverted will see this.
I'm the guy who greatly expanded that table about various patterns of 29 and 30 months to attempt to keep with the actual synodic months. I calculated and added the data about how long (in years and days) each period is; I calculated and added the information about how many 30 day months and how many 29  day months there would need to be to make up the period; and where the original table had said on that after this much time you'd be about a day off, I figured out and stated whether that would be a day ahead or behind.  I hope it was not original research; I did not come up with the original continuing fractions in the first place (I didn't know about it), and the rest was basic high school algebra.
That IP user figured out (not difficult) the time for the last pattern to fall one day off (assuming that the moon never changes its orbit--which of course it does).  (S/he then went to rather a lot of trouble putting it in--getting it to format suitably; more on that in a bit.)
When I saw that, I had in mind to add a note to the table to the effect that the figure was hypothetical, assuming that the moon's orbit will stay constant over millennia--and in fact it wouldn't be accurate.  Do you have any strong feelings on that?
And to the IP user--I hope you're seeing this.  I, too, when I'm editing something with complicated formatting (and feeling my way around to do so), find myself editing many times before it comes out the way I had in mind (sometimes, before it comes out at all!).  So I make MUCH use of the "Show preview" button.  It's next to the "Publish changes" button.  And it shows you, above the edit window, what your changes will look like if you save (publish) them.  That way, I don't add a lot of edit history--some of which (at least for me) would have come out as garbled gibberish.  When I get it more or less the way I had in mind, and it looks OK, THEN I publish the changes. Uporządnicki (talk) 18:53, 8 November 2020 (UTC)
thread_title:  The edit revert at the table of 29/30 day months 

message: That Spanish "lunar calendar" for 2017 pictured at the top of the article might very well be for 2017, and it might even be Spanish--but it's not a lunar calendar, at least not in the sense described in the article.  It is simply a schedule of the phases of the moon set against their dates on the standard Gregorian calendar. Uporządnicki (talk) 03:19, 12 November 2020 (UTC)
thread_title:  Spanish "lunar calendar" 

message: I did some serious work concerning that table about patterns of months to accomplish an accurate lunar calendar; I substantially expanded the text explaining it all.
I was hoping for comments and/or improvements from others, and I said as much in my explanation of my edit, with the idea that it would show up on the Watchlist of anybody watching this article.
Unfortunately, I then went back in and fixed a trivial spacing glitch in the edit I'd just worked on.  I suppose because I did it just two minutes later, it's that trivial edit and not the substantial one that shows up on the Watchlist (or at least on mine).  So here is my notification to anybody interested who is paying attention.  Uporządnicki (talk) 13:45, 12 November 2020 (UTC)
thread_title:  Serious work re that table--not in Watchlists? 

message: Reading the article on "Ancient and Medieval Values for the Mean Synodic Month" made me question my sloppy usage "long-term". 100 years? 1000 years? a million? a billion? Obviously not, but "modern" isn't great either. Can anyone suggest a better wording?
:Chapront-Touzé & Chapront's paper (see above) is claimed to be valid for several thousands of years, so "long-term" would be a few thousand years. AstroLynx (talk) 12:03, 30 April 2021 (UTC)
replies: text: Yes, I can see that but my question is about the present day approximation of 29.53059: what are its limits? 19002100? 15002500? Even if I do the maths, it'll be OR without a citation. Anyone? --John Maynard Friedman (talk) 17:32, 30 April 2021 (UTC)
thread_title: 'Long-term' average <sharp intake of breath>

message: Someone added a "citation needed" thingie to my edit about the length of a cycle in the tabular islamic calendar.  But that comes from simple arithmetic. Uporządnicki (talk) 10:10, 12 May 2021 (UTC)
replies: text: Ah!  Now I see, too, that someone also added a tag about Original Research to the entire section.  I'm responsible for maybe a third to a half of the table that is the main point of that section.  Initially I started examining it and playing with it because I (and at least one other person) were having trouble figuring out what it was all about.  I set out to make it clearer, and then wound up expanding it considerably.  I added several columns.  (I also clarified and expanded what had been--as I saw it--a rather cryptic statement on the Tabular Islamic Calendar.)  The data I added came from arithmetic, and a little very basic high school algebra.  When I was working on it, I did worry about Original Research.  I inquired somewhere (I don't remember if it was here or at some project page) whether that would intrude on OR territory.  Someone directed me to some guideline that suggested that just doing some basic math on data available from somewhere is permissible.  , I think this might involve you, but I'm not sure.  Uporządnicki (talk) 13:23, 12 May 2021 (UTC)
replies: text: Yes, there is an exception to the OR rule for basic arithmetic. What made me concerned was that it such a large section without independent sources. It is not a show stopper but it would certainly improve its credibility. You probably saw an earlier discussion about the length of a mean synodic month, where someone did some independent calculations to reach a figure that was unjustifiably precise, as the WP:RS source demonstrated. Hence the concern. If no-one else shares it, you can remove the tags. --John Maynard Friedman (talk) 14:00, 12 May 2021 (UTC)
replies: text: , do you have an opinion on this? --John Maynard Friedman (talk) 10:52, 13 May 2021 (UTC)
replies: text: The table demonstrates how increasingly accurate ratio's for the synodic month can be obtained from a continued-fractions analysis but the table does not explain the cycles commonly found in lunar or luni-solar calendars. The larger periods can perhaps be interesting for the makers of mechanical planetaria (Antikythera Mechanism, etc.) or astronomical clocks (Jens Olsen's World Clock, etc.) but for calendars they are too awkward. AstroLynx (talk) 13:16, 13 May 2021 (UTC)
thread_title:  Citation needed for arithmetic? 

message: The period of 12 lunations you're talking about is just mimicking the year of the Earth around the sun. Real lunar calendars don't have that. Also, an Earth month can't be divided into 29 or 30 days, it should be divided into about 28 nights. A night is similar to a day, but related to the moon. 2404:3C00:502F:4C80:75C8:D2CC:2F81:97B0 (talk) 04:41, 4 September 2021 (UTC)
replies: text: It seems that you want to reinvent the lunar calendar to what you feel it should be.  Fair enough!  Invent one and promulgate it.  If it gains enough footing to warrant discussion and description in independent sources, it might get its own Wikipedia article. Uporządnicki (talk) 12:26, 4 September 2021 (UTC)
thread_title:  Lunar or Lunisolar 

message: In the intro, why is there so much emphasis for a Japanese calendar? like a whole paragraph. Did the Japanese calendar influence other nations? If any country ever deserves some emphasis in the intro. It should be China considering their lunar calendar heavily influenced East Asia in whole. Yet not even a single dedicated sentence was spared for China in the intro. Despite the Chinese calendar is undoubtedly the most important calendar CONSIDERING it is the "mother" that was adopted by many other Asian countries. It is probably the most influential calendar second to the Gregorian calendar. I added a single sentence stating that a number of East Asian countries strongly based their traditional lunar calendar on the original Chinese calendar.SoyDream888 (talk) 06:48, 20 January 2023 (UTC)
replies: text: Yes, you were correct about it being WP:UNDUE but for the wrong reason: there were two large paragraphs about lunisolar calendars in the lead that were undue because they were way off topic. Lunisolar calendars certainly need to be covered in the body but one or two sentences in the lead is all that WP:LEAD requires to summarise of one small section. --𝕁𝕄𝔽 (talk) 13:16, 20 January 2023 (UTC)
thread_title:  Undue weighted introduction 

message: The Haida Calendar link redirects to the Haida page. However, it appears discussion of their lunar calendar has been removed from that page. Does anyone know why it was removed and if it now exists somewhere else? If it is merely gone, then the Haida Calendar should probably be deleted from the examples. 73.210.187.84 (talk) 14:31, 11 June 2023 (UTC)
replies: text: as it hasn't appeared on the Haida people page on at least the last 18 months. --𝕁𝕄𝔽 (talk) 14:39, 11 June 2023 (UTC)
thread_title:  Discussion of Haida Calendar Removed from Haida Page 

message: Open to 𝕁𝕄𝔽.  You do realize you've broken my heart, right? Uporządnicki (talk) 22:02, 6 January 2024 (UTC)
thread_title:  Length of lunar month 

message: The current lead image (Iran Kalender 1863 Linden-Museum.jpg) is an Iranian calendar so it seems probable that it is a Shia solar Hijri calendar rather than a Sunni lunar Hijri calendar. If so, then it is not appropriate for this article. Does anyone know for certain? 𝕁𝕄𝔽 (talk) 07:17, 19 April 2024 (UTC)
replies: text: Given that months in the lunar Hijri calendar are traditionally determined by actual observation, I think it almost certain that this is a solar calendar, so I have deleted it. The only slight doubt is that it could be a Tabular Islamic calendar but nothing in the file description suggests that it is. --𝕁𝕄𝔽 (talk) 12:17, 19 April 2024 (UTC)
thread_title:  Is the lead image appropriate?