Talk:Blue moon

A note
The information from Full moon should probably merged into this article. Blank Verse  &empty;  16:26, 11 Apr 2005 (UTC)

blue ship?
The term "Once in a Blue Moon" has nothing to do with the cyclical appearance of a celestial body that we call the moon. It is actually associated with an early Dutch trading ship known as the "Blue Moon." The Blue Moon was a world travelling trader and had a planned route to follow as it traversed the world's oceans. The Dutch captain at the helm had to make decisions as to where they went based on directions from home to sell or to buy certain items in specific ports. What made their appearance so rare in some ports was the captains discretion to buy more of some goods because it was a good price. His holds were full and he now had to interrupt his planned or promised route to resell his new found purchases. When he finally got back to the original schedule of his trade route --- IT WAS ONCE IN A BLUE MOON --- Hence that is where the term originated - not because of an imagined ethnic variety of our "man in the moon." —Preceding unsigned comment added by Jimcorbett (talk • contribs) 18:04, 7 September 2007 (UTC)
 * I put this item under a header below the administrative headings. Is there a source for this story?! -- Tom Peters (talk) 15:03, 31 December 2009 (UTC)
 * I have done research on this. I have looked through every publication I could find available to the public. I can find no reference to a Dutch ship named 'The Blue Moon', whether that ship be a trader, schooner, sailing ship or any other ship known as, manufactured, flagged or owned under a Dutch registry. Further research in archaic foreign flag archives would be necessary. The only ships with the name Blue Moon that I found were the Tennessee River Blue Moon Cruises, the former Pallmantur Cruises MS Blue Moon, currently registered as Azamara Cruises MS Azamara Quest. MR2David (talk) 07:45, 19 August 2013 (UTC)


 * Someone has a sense of humor! Zaslav (talk) 05:37, 21 August 2013 (UTC)

Truly blue?

 * Those definitions of a "blue moon" are of a recent date as the original definition that gave rise to the phrase "once in a blue moon" has been generally forgotten. The original definition related to the moon actually being blue. This occurs when Venus is very close to the Earth and geocentricly on the opposite side of the Moon from the Sun and the sky is very clear. The dark part of the Moon is then illuminated by Venus and appears to be a pale blue color.

I've removed this text from the article Esbat, as it strikes me as being very unlikely -- the full Venus doesn't give off much light -- certainly less than the Earth. Can anyone comment on this?

The Venus explanation is nonsense - Venus is simply not bright enough to illuminate the moon. However, the following explanation of a Blue Moon is one I've heard before; "Although a 'blue moon' doesn't really look blue, there have been times when the moon does seem to have a blue color. This can be caused by dust particles in the atmosphere, which scatter light. The effects of this dust on the light coming from the moon can cause it to appear bluish in color. Fine dust particles are ejected into the Earth's upper atmosphere after large volcanic eruptions, for example. The eruption of the Krakatoa volcano in 1883 gave us one such 'blue moon'. For about 24 months after this volcano exploded, the dust it spewed into the upper atmosphere caused the moon to appear green and blue when viewed from around the world. " (Source) Denni &#9775; 2005 July 7 19:35 (UTC)


 * I put this item under a header below the administrative headings. -- Tom Peters (talk) 15:03, 31 December 2009 (UTC)

I always thought the phrase "once in a blue moon" did actually refer to the coloration of the moon due to a rare size distribution or aerosols (or smoke). This seems to be the origin of this phrase in the common vernacular, at least originally. Perhaps more recently the astronomical definition came more into play. Should the "true" origin be featured more prominently in the article? I will put this into the article with supporting references that would help back this up. Here is one to consider: — Preceding unsigned comment added by 67.6.130.136 (talk) 15:02, 18 January 2015 (UTC)
 * I see my edit was reverted due to "incorrect interpretation of sources". However the sources do state that the "once in a blue moon" phrase did originally come about from the rare coloration phenomenon. Somehow the multiple history of definitions should be more prominently featured in the article, especially to remember more original definitions of things. — Preceding unsigned comment added by 67.6.130.136 (talk) 16:25, 18 January 2015 (UTC)
 * Here I quote from one of the references I cited. Where is my misinterpretation in the following? 'So, by the mid-19th century, it was clear that visibly blue Moons, though rare, did happen from time to time — whence the phrase "once in a blue Moon." It meant then exactly what it means today, a fairly infrequent event, not quite regular enough to pinpoint. That's meaning number four, and today it is still the main one.'

- See more at: http://www.skyandtelescope.com/observing/once-in-a-blue-moon/#sthash.Ky92kCu0.dpuf"

the article states that the moon has appeared blue, but not that that is the origin (or has ever been the intended meaning) of the phrase "blue moon" compare it to when pigs fly, the fact that the moon can actually appear blue is coincidence. Deunanknute (talk) 16:42, 18 January 2015 (UTC)
 * I just saw your comment that was made simultaneous to my reinserting my article changes. The sentence I'm quoting above does say the phrase "once in a blue moon" arose from the coloration effect, and wouldn't be a pure coincidence. So at least there should be multiple things mentioned in the definition from what I can interpret. It would be the "calendrical" blue moon and "literal" blue moon. — Preceding unsigned comment added by 67.6.130.136 (talk) 16:45, 18 January 2015 (UTC)

''In fact, the very earliest uses of the term were remarkably like saying the Moon is made of green cheese. Both were obvious absurdities, about which there could be no doubt. "He would argue the Moon was blue" was taken by the average person of the 16th century as we take "He'd argue that black is white."'' second paragraph mentions usage of "blue moon" as an absurdity in the 16th century, it goes on to mention the moon appearing blue in 1883 200-300 years later Deunanknute (talk) 16:53, 18 January 2015 (UTC)


 * Yes there are the even earlier "absurd" definitions. However the "once in a blue moon" phrase at least literally refers to a rare occurrence and not and absurd one. It matches up better with the rarity of the real atmospheric coloration effect and is directly connected in the source I'm quoting above. The color effect is also mentioned elsewhere in my various sources. Thus I think it merits some consideration in the definitions section. — Preceding unsigned comment added by 67.6.130.136 (talk) 17:00, 18 January 2015 (UTC)

which is already mentioned under Blue_moon and under Blue_moon as "Owing to the rarity of a blue moon, the term "blue moon" is used colloquially to mean a rare event, as in the phrase "once in a blue moon"" — Preceding unsigned comment added by Deunanknute (talk • contribs) 17:10, 18 January 2015 (UTC)


 * However, the atmospheric coloration aspect isn't mentioned in the Definitions section in case you are implying that it is. Here by the way is another reference with the visibly blue moon — Preceding unsigned comment added by 67.6.130.136 (talk) 17:17, 18 January 2015 (UTC)

The Definitions section mentions the term "once in a blue moon" as referring to it's rarity. The Visibility section talks about the fact that the moon can literally appear blue. The phrase "once in a blue moon" does not owe its origins to the fact that the moon can sometimes appear blue. These two facts are separate from each other. Deunanknute (talk) 17:27, 18 January 2015 (UTC)


 * The use of the word "whence" in my reference quote seems to contradict the assertion that they are separate. — Preceding unsigned comment added by 67.6.130.136 (talk) 18:01, 18 January 2015 (UTC)

Your proposed edit states that the term "blue moon" originated with the moon appearing blue. This is false. The first known use of "blue moon" was in 1528, referring to an impossibility. The first known use of "once in a blue moon"[sic] was in 1821, referring to a rare event. Deunanknute (talk) 18:17, 18 January 2015 (UTC)


 * Perhaps there's a better way to reword my edit to indicate the origin of the phrase "Once in a blue moon" and that over history this has been a common connotation of a "Blue Moon"? — Preceding unsigned comment added by 67.6.130.136 (talk) 18:21, 18 January 2015 (UTC)

you have no evidence that the phrase "once in a blue moon" originally referred to a blue color moon Deunanknute (talk) 18:29, 18 January 2015 (UTC)


 * I would submit there is evidence in this quote - 'So, by the mid-19th century, it was clear that visibly blue Moons, though rare, did happen from time to time — whence the phrase "once in a blue Moon." ' It is also suggested in this reference that I quote here: 'Some observers have reported seeing blue-colored moons, such as that seen from Hawaii in August, 1991, not long after the eruption of Mt. Pinatubo in the Philippines. Volcanic dust in the air -- or smoke from a forest fire -- can make a moon appear blue in color. But these blue-colored moons are rare. They might have inspired the expression "once in a blue moon."' 67.6.130.136 (talk) 18:48, 18 January 2015 (UTC)

"once in a blue moon" originated from "blue moon" meaning never I think the author you are linking merely assumed the connection https://books.google.com/books?id=h_AIAAAAQAAJ&pg=PA228&dq=%22blue+moon%22&hl=en&sa=X&ei=3wC8VJLfOIShNoSwhNAD&ved=0CDwQ6AEwBDisAg#v=onepage&q=%22blue%20moon%22&f=false https://books.google.com/books?id=u0EqAAAAYAAJ&pg=PA78&dq=%22blue+moon%22&hl=en&sa=X&ei=HgG8VOC2FcHvggSU04OAAw&ved=0CCUQ6AEwADiiAg#v=onepage&q=%22blue%20moon%22&f=false https://books.google.com/books?id=GXxcAAAAcAAJ&pg=PA89&dq=%22once+in+a+blue+moon%22&hl=en&sa=X&ei=cgK8VNqcEcOgNqyFg9gB&ved=0CBwQ6AEwADjmAQ#v=onepage&q=%22once%20in%20a%20blue%20moon%22&f=false Deunanknute (talk) 19:05, 18 January 2015 (UTC)

Are both authors incorrect then? I think these are two authors who are looking at the overall historical evolution of the multiple definitions. It is hard for me to ignore the "literal" coloration as part of this history of the definition of the Blue Moon and of "Once in a Blue Moon". Sorry if this seems confusing, but I might ask if the purpose of this article is to talk about the "never" occurring Blue Moon, then why talk about the calendrical recurring one? At least one might find a way to discuss this more completely in the definition section? Maybe the definition should mention three main items in historic sequence: 1) The earliest "absurd" one. 2) The once in a blue moon atmospheric color. 3) The calendrical interpretation more recently emphasized. — Preceding unsigned comment added by 67.6.130.136 (talk) 19:14, 18 January 2015 (UTC)

The article is about both - they are the same "blue moon" originally meant "never", then it was later used as "very rarely" (much as we do with the word never today) separately "belewe" (betrayer) moon was used to describe the 4th moon in a season, it betrays by making you think the season is over "belewe" sounds like "blue" and the 4th moon started to be called "blue" (again, there are many examples today) but, there is no evidence that the origin of the phrase "blue moon" has anything to do with actual color, except in assumed etymology https://books.google.com/books?id=vPgIAAAAQAAJ&pg=PA328&dq=%22once+in+a+blue+moon%22&hl=en&sa=X&ei=uwW8VPGaB8OkNqHCgOgF&ved=0CC0Q6AEwAzi0AQ#v=onepage&q=%22once%20in%20a%20blue%20moon%22&f=false Deunanknute (talk) 19:32, 18 January 2015 (UTC)

On the other hand, here is another reference from a respected weather magazine that discusses the two main uses of the "blue moon" term, in the meteorological and astronomical communities. They both seem legitimate here with favor to the atmospheric one: http://www.weatherwise.org/Archives/Back%20Issues/2009/Sept-Oct%202009/full-Gedzelman.html — Preceding unsigned comment added by 67.6.130.136 (talk) 19:43, 18 January 2015 (UTC)

That article gives no evidence for "blue moon" originating with apparent color due to atmospheric effects. It does mention the first usage, which in context meant something impossible. the article states “But the popular meaning of the expression refers both to color and to something unusual.”, but gives no further evidence. Deunanknute (talk) 20:08, 18 January 2015 (UTC)

We do have something of an "authority", folklorist Philip Hiscock who is stating the connection from the color effect to the Blue Moon expression in the 19th century. "Even by the nineteenth century it was clear that although visually blue moons were rare, they did happen from time to time. So the phrase "once in a blue moon" came about. " This seems to me again important enough to recognize more in the definition. http://webs.wichita.edu/lapo/blumoon.htm — Preceding unsigned comment added by 67.6.130.136 (talk) 20:32, 18 January 2015 (UTC)

that's just a copy of your other source http://www.skyandtelescope.com/observing/once-in-a-blue-moon/ Deunanknute (talk) 20:37, 18 January 2015 (UTC)


 * Yes it is the same author, though here it is stated more unambiguously the point I'm making, and I'm pointing out this is an authoritative source. It seems hard for me to reject this out of hand.


 * I did a lot of study/work on this article a long time ago and I seem to remember that in all of my searches I could not come up with more info than what we've got for the first use of the term. I consider it very flimsy evidence and agree that it would be appropriate to include alternate theories if there are any.  I at first knee-jerked a NO reaction to 67 but s/he is starting to win me over, though I don't have the time right now to read the sources s/he has presented...though I've most likely read them all already in the past as I read everything.  But there is always a way to see things in a new light and realize that you've missed something.  67, if you have the time and energy, could you present something you'd like to add?  Thanks for your work.  This article, like the rainbow article that I also watch, gathers a lot of editors that come by and figure that we've got everything all wrong, so please be patient with us? :)  Gandydancer (talk) 20:41, 18 January 2015 (UTC)


 * OK I'll try to introduce some of my edit once again. Please try to modify my edit if you think I'm misstating something instead of erasing the whole thing. Thanks much for your consideration. By the way my own background is in both meteorology and astronomy so I like to consider both aspects. — Preceding unsigned comment added by 67.6.130.136 (talk) 20:44, 18 January 2015 (UTC)


 * Thanks. I reverted because I'm pretty sure that you are not correct.  I'm sorry but I just don't have the time right now to get into this and give it the thought that it deserves.  Perhaps a new editor will come along and add to the discussion.  For me, I will need to take time to go over it again before I agree with you.  Gandydancer (talk) 21:11, 18 January 2015 (UTC)


 * OK - I will look forward to your further consideration and possibly with additional editors. — Preceding unsigned comment added by 67.6.130.136 (talk) 22:19, 18 January 2015 (UTC)

Apogee and full moon ?
maybe once in a blue moon someone will look at this talk page.

I have once read that a "blue moon" refer to a full moon that also occur when the moon is in apogee (the furthest away from earth) this is a combination that only occur about every 50 ? years. Could not find any refrence to it anywhere.

can anyone help ?

As far as I remember there was such a "blue moon" few years ago. The moon was 15% smaller (as seen from earth)

Does this ring a bell to anyone or "what was I smoking?" is the better question to ask ? Zeq 20:33, 12 October 2005 (UTC)

BTW the full moon apogee is at 2014 so may it is every 19-20 years Zeq 20:37, 12 October 2005 (UTC)

So..... No one care about this ? only middle east articles get frequest visits ? Zeq 17:28, 14 October 2005 (UTC)


 * I've never heard of that use of the term "blue moon". --Carnildo 18:57, 14 October 2005 (UTC)

Why the wrong lemma ?
Shouldn't it be Blue Moon ? -- 141.30.212.78 20:25, 3 April 2006 (UTC)


 * Is it wrongly capitalised? It could be, if this may refer to an occurrence when the Moon is blue.  However, (1) the Moon itself is not blue even during the atmospheric event; and (2) an appearance of the Moon (the Earth's only moon), is conventionally written as "a moon", hence the related article title full moon.  See MOS:CELESTIALBODIES.  The lemma is supposed to represent common usage, as in  and  which have "blue moon", so I think Blue moon as at present is preferred. --Cedderstk 12:26, 3 August 2015 (UTC)

What is the purpose of the section "Calendar vs. Farmers' Almanac: 2004 – 2010"?
I can not understand at all what the rationale is for the section "Calendar vs. Farmers' Almanac: 2004 – 2010". Could someone please explain this to me? Lunokhod 22:00, 12 January 2007 (UTC)

A number of Pagan beliefs rely heavily on specific interpretation of the lunar cycle. The difference is important, as it determines when the named moons occur and can be celebrated. Bards 20:22, 16 February 2007 (UTC)

I see the section has been renamed, but it's still not the greatest. The difference is between being a strictly astronomical phenomenon (unfortunately referred to with the Farmer tag) that is the same everywhere on Earth, and being an artifact of calendars and timezones and therefore happening at different dates in different places.

It would be nice if this whole article were rewritten using the objective Astronomical definition as the standard, with only one specific section to describe the Sky&Telescope misinterpretation of the Farmer's Almanac that introduced the subjective Calendar definition.

Pictures?
Does anyone have a picture of a blue moon? Quietmartialartist 00:42, 7 June 2007 (UTC)

I do. Reply on my talk page if you want me to give you the URL (seeing that I do not know how to put pictures on articles). Chimchar monferno (talk) 04:41, 26 February 2008 (UTC)

Seasons for Farmer's Almanac
Hi 199.33,

This page defined seasons as 3 months, starting on March 22 etc (but I'm not sure where that came from) This is consistent with North American seasons (ie: Winter starts on Dec 22), and that's how I explained it in the text.

However, your definition has the first Winter moon starting anywhere from 7th Dec to 5 Jan (and I'm not sure where that came from) .... and we're now contradicting ourselves. Do you have a source for the info we can add so we know which is right? Greg (talk) 19:27, 31 January 2008 (UTC)

The Winter solstice is 12/21. The new moon nearest that is the Early Winter moon. So it's right to say that the Early Winter moon can start almost 2 weeks before, or almost 2 weeks after, the solstice. (199.33)  —Preceding unsigned comment added by 199.33.137.2 (talk) 17:41, 15 October 2008 (UTC)

Oh, it also contradicts the dates of blue moons - all those dates are on or around the 21st of the month... to do that the seasons must start on or around the 21st of the month (2 months prior). Greg (talk) 19:41, 31 January 2008 (UTC)

Sky and Telescope confirms the moon dates. Greg (talk) 19:49, 31 January 2008 (UTC)

I see you're talking about "New Moon" which starts 14 days before the solstice, and which leaves "full moon" to occur on or after the solstice. Does this make it more complicated!?!? Greg (talk) 20:52, 31 January 2008 (UTC)

The Farmer's Almanac was directed towards farmers. They were very interested in knowing which seasons happened on which dates. There are certain crops that need to be planted in the early spring, and other crops in either mid or late spring. The same thing applies to harvest times. Farmers need to plan ahead to get laborers, etc... Having an almanac that showed these seasons was great. For example, the early spring showed the 4 weeks on the calendar that was for planting early spring crops. The late summer moon shows the times to reserve the laborers for harvesting the particular crops that will be ripe in the late summer. So it wasn't just the full moon, but rather the entire 4 week period that was important.

Aside from farming (I'm not a farmer) I think it is romantic to be able to look at the moon on any day and know which moon it is. Today is 2/28. Looking at the moon today I know that it is the late winter moon. Soon it will turn into the early spring moon. Isn't the moon a great way to get excited about Spring? Doesn't this make the moon seasons, and the blue moons, more relevant to everyone, including those that are not farmers?

I'll add the dates of the seasons for 2008 to the article. Would it be too difficult for someone to set up the front page of Wikipeida to automatically display which season it is for each day? For example: Today is 2/28. It should display "Late Winter moon" somewhere on the front page. On 3/6 it would automatically switch to "Early Spring moon". I think a lot of people would like this convenient track of the seasons. —Preceding unsigned comment added by 199.33.137.2 (talk) 18:03, 28 February 2008 (UTC)

Having the current cycle would be great. I don't think wikipedia can do it... I hae to run now, but may take a quick look at "phases of the moon" or similar here - because if it's possible, that page will have done that eh?? Greg (talk) 22:53, 27 March 2008 (UTC)


 * I disagree with the naming of the lunations supposedly "according to the Famer's Almanac"; specifically, applying the rule to New Moons and name the lunations accordingly. The text refers to "this convention", but is there any actual evidence that this convention used to be followed?  In contrast, I see that conventional names (Harvest Moon, Hunter's Moon, Easter Moon) refer to Full Moons, so e.g. the Easter Moon is the first Full Moon after the aequinox, not the Full Moon of the first lunation that had its New Moon after the aequinox.  See Full_moon.  I propose to edit the list for 2010 accordingly for Full Moons and do away with this supposed New Moon convention. -- Tom Peters (talk) 15:22, 31 December 2009 (UTC)


 * The Summer Solstice is traditionally known as Midsummer's Day in England, hence it was conceived of as the middle not the beginning of Summer. I think it is an American innovation (possibly by Benjamin Franklin) to treat solstices and equinoxes as the startpoint of seasons. Therefore it is incorrect to use this reckoning as a basis for determining blue moons as if it is universal.--Jack Upland (talk) 00:34, 28 December 2009 (UTC)

There is a contradiction in the discussion of blue moons for 2012. There is a long quote stating that there is no blue moon in 2012, in spite of there being 13 moons in 2012, because the final moon is after the solstice. By this calculation the blue moon is August 21, 2013. This agrees with, for instance, or even the Sky & Telescope article. However, if you go to the Farmers Almanac it places the blue moon in 2012. Note that the astronomical articles all reference the 'old' or the 'Maine' Farmers Almanac, which leads us to believe that the 'new' Farmers Almanac is using some other system - actually probably using calendar years instead of the astronomical seasons. Dgsteig (talk) 11:25, 1 August 2012 (UTC)
 * The article shows that there are two different conventions in discussing blue moons. The Maine Farmers' Almanac was discussing full moons in a season, not in a calendar month.


 * In 2012, no season had four full moons, so under the Maine Farmers' Almanac rule, there would be no blue moon.


 * However, under the Sky & Telescope rule, the calendar month of August 2012 had two full moons (except in the central Pacific Ocean region just west of the International Date Line, where it was September 2012 that had two full moons), and the second of these would be called the blue moon.


 * On the other hand, the summer of 2013, which starts on June 21, 1:04 A.M. EDT and ends on Sept. 22, 4:44 P.M. EDT, has four full moons, as seen in this list from the Farmers' Almanac (all in Eastern Daylight Time or EDT):


 * June 23, 7:32 A.M. Full Strawberry Moon
 * July 22, 2:16 P.M. Full Thunder Moon
 * Aug. 20, 9:45 P.M. Full Sturgeon Moon
 * Sept 19, 7:13 A.M. Full Harvest Moon


 * Again using the Maine Farmers' Almanac rule, these could be called the early summer, middle summer, blue summer, and late summer full moons.
 * I hope this helps explain the difference in blue moon conventions. — Glenn L (talk) 00:16, 10 November 2012 (UTC)

Belewe, Christianity, & Easter
It appears that Belewe also means "Betrayer" in old english.

So when the people in the 1300s said "If they say the moon is Belewe, we must believe it's true" would have a double meaning of "if the church say it's a betrayer moon, rather than the real season, we have to take their word for it".

Combine that with the church's focus on the computus - where Easter MUST fall on the first sunday after the easter-based full moon.

So the late winter moon is the moon for Lent (Lenten Moon - lent begins on the first day of the new Lent moon), the early spring moon is the moon for Easter. Note that the Farmer's Almanac definition then fits this calculation - those moons always retain their names. And the moon before Lent MIGHT get confused as being the Lent moon, and it would be the clergy saying "that's not the lent moon, that's the betrayer moon".

Just thoughts... putting together lots of little facts :-) Greg (talk) 20:51, 31 January 2008 (UTC)

This has info on blue moon dates, and that calculations of Farmer's Almanac are based on the nominal vernal equinox (21 March) (not the real vernal equinox, nor the december/winter solstice).

Farmers Almanac says that Belewe means "to betray" in Old English and supposes the concept is linked to an extra moon.

Greg (talk) 21:31, 31 January 2008 (UTC)


 * There are several problems with this:
 * "Belewe" meant "betray", not "betrayer". There appears to be no evidence for the phrase "betrayer moon": it's merely speculative induction.
 * This interpretation makes no sense in the context of the original rhyme. The couplet should be an attack on the clergy, not a bland statement about the calendar.
 * The date of Easter was not calculated by "clergy" on an ad hoc basis. It was determined as part of long-range calculations of the calendar on a global basis (although there were successive, competing methods), not in England. Hence there is no reason for there to be an English term for "betrayer moon". If this was a genuine concept, the term would be in Latin.
 * The astronomical anchor for the date of Easter is the vernal equinox, not the Lenten moon anyway.--Jack Upland (talk) 19:56, 29 December 2009 (UTC)


 * Jack, I cannot comment on the use of a verb as an adjective in Middle English, but your other 3 points are invalid. Greg's proposal makes complete sense and incidentally suggests that the original meaning was different from that of the Farmer's Almanac.
 * Easter is computed by conventional rules, which only approximately match the actual phase of the Moon and the actual time of season; for example, the begin of Spring for the purpose of Easter was fixed on 21 March in the Julian calendar, NOT the actual astronomical aequinox as you claim in your last point. By the 8th century a fixed 532-year Easter cycle based on the 19-year Metonic cycle had been established.  However, it drifts from reality by about 1 day in 3 centuries.  Moreover, the solar Julian calendar drifts through the seasons by 1 day in about 131 years.  So by the 16th century, before the Gregorian reform, the calendar was in total dis-array.  Easter was supposed to be celebrated on the first Sunday after the first Full Moon of Spring.  Between Mardigras and Easter day, people had to fast - which was a necessity anyway because there was little to eat in Winter.  So people were really looking forward to the end of this Lent period, and they would know by experience when Spring had come to life, and could watch an obvious Full Moon easily.  I compared the traditionally computed Easter Full Moons with the actual ones, and find that in the early 16th century, 4 times in every 19-year cycle, the computed ecclesiastic Full Moon was 1 month later than the actual Full Moon that fell after the actual Spring aequinox; so Easter was delayed by a full month in obvious conflict with observable reality.  I suppose that priests called such an early actual Spring Full Moon a "betrayer Moon".  In response, people mocked the priests for their obvious incompetence to compute Easter correctly.  So the rhyme is anti-clergical, to address your second point.
 * If this explanation is correct, then the "Blue Moon" is actually the first observed Full Moon in the Spring season, that falls before the Easter Full Moon as computed by the old (Dyonisian) computus for the Julian calendar. When looking from the ecclesiastic year, it is always the last Full Moon of the Winter season that runs from 21 Dec. to 21 March in the Julian calendar, which may be the 3rd or 4th Full Moon in that period.  It can never be the 3rd in a 4-Moon season as the Farmer's almanac will have it.  Even if you count a prolonged season from the actual Winter solstice to 21 March in the Julian calendar, then the ecclesiastic Easter Moon is still the first Full Moon of the Spring season, not the 4th of the Winter season; and the "betrayer Moon" is the last Full Moon of the Julian calendar Winter season.
 * -- Tom Peters (talk) 14:48, 31 December 2009 (UTC)


 * "I cannot comment on the use of a verb as an adjective in Middle English". "Betrayer" is a noun, not an adjective, and you 'could' produce an independent source that says "belewe" means "betrayer", not "betray". If there was one.
 * "Easter is computed by conventional rules". Precisely. And the conventional rules were international and long-term. The image conjured up in the article, and in your comments, of English priests making their own calls of when Easter fell by whimsically labelling particular moons as "betrayer moons" is a ridiculous fantasy. So to put it in a nutshell: the moons had no significance, and there is no reason for them to have an English name if they did - they should have a Latin name.
 * "I suppose that priests called such an early actual Spring Full Moon a 'betrayer Moon'." There is no evidence that the term "betrayer moon" was ever used. Given that, as you say, the English Church was using the erroneous Gregorian calendar, there was no reason for the priests to make lunar observations: they were just determining Easter from previous calculations.--Jack Upland (talk) 09:04, 12 January 2010 (UTC)

This etymology of "belewe" comes from Old English 'be' (transitive prefix) + 'læwan' (to betray); however interesting, this is utterly pointless unless one can produce any credible evidence that "blue" (c.1300, bleu, blwe, etc., from O.Fr. blo, Frankish *blao, from P.Gmc. *blæwaz [cf. O.E. blaw, O.S., O.H.G. blao, Dan. blaa, Swed. blå, O.Fris. blau, M.Du. bla, Du. blauw, Ger. blau], from PIE *bhle-was) was ever acceptably spelled "belewe". See Etymology Online entry: 'blue' and Old English: be-, blǽ-hǽwen, be-lǽwan Garris0n (talk) 04:35, 29 August 2011 (UTC)


 * Very simply put each quarter of the year has 3 full moons, one per month. Therefore, the moons have been typically named "Early/Mid/Late Spring, Summer, etc. Moon." Because there are 13 full moons within the year, there will always be one quarter with 4 full moons. The odd moon is listed between the mid and late moons and is called the Blue Moon. The term Belewe means "betrays" because the odd moon betrays the schedule of 3 moons per quarter. Although it is undocumented, legend states that Blue Moon is a form of the name Belewe Moon.
 * * I've seen several references to Easter when discussing the Blue Moon. The Blue Moon will never have an effect on how Easter falls in the calendar. Easter is always the first Sunday after the first full moon that occurs after March 21. That full moon is always the normal Early Spring Moon. A Blue Moon during the spring would always fall in May, thus having no influence on Easter. MR2David (talk) 08:48, 19 August 2013 (UTC)

Lunar Cycle Time
Last I checked the moon took about 28 days to make a full cycle. That would make 13 full moons per year. I have also heard the wide told tale that a blue moon was the second full moon of a Gregorian Calendar month, but it occurs 1-2 times per year, not once every couple of years. —Preceding unsigned comment added by 70.106.3.58 (talk) 20:47, 3 March 2008 (UTC)


 * Actually, it takes about 27.5 days. Yes, the Blue Moon is the second full moon in a month. If I can just get my science fair display board back, I can see how many full moons there are in a year, although I'm pretty sure that's correct.Chimchar monferno (talk) 08:29, 20 March 2008 (UTC)


 * For anyone reading this - note that it takes 27.5 days to get back to the same spot, but in that time the earth has gone 1/12 of the way around the sun, so it takes a little longer before you would actually see the sun on the moon at the same angle... which is where 29/30 days comes in. Greg (talk) 08:02, 22 April 2009 (UTC)

Just look at the list of blue moons in the 10 year period in this article. There are 4 (no matter which way it's counted). There are occassionally an extra 2 blue moons if the calendar definition is used, when no full moon falls in February at all (black moon). Greg (talk) 22:52, 27 March 2008 (UTC)

Would it be correct to place information regarding the use of blue moons in movies, books and television? For instance, I know that the show Charmed had an episode that revolved around the sisters turning into beasts due to the blue moon. 208.242.14.183 (talk) 20:17, 18 September 2008 (UTC)


 * Random lists of trivia have no proper place in an encyclopedia. If you feel that references to blue moons in these media are worth discussing in this article, then add a paragraph or two discussing them, but make sure that what you write really is a discussion in real English prose, not a merely a listing of those references. Also make sure your assertions are well-sourced. TheScotch (talk) 06:45, 31 July 2015 (UTC)

confusion in the introduction
I resolved some confusion that had accumulated in the introduction. Someone had apparently divided the average period between two blue moons by 365 days (instead of 365 + x) and anonymously added the resulting number of years with lots and lots of digits but no reference; then someone else had taken this value at face value and anonymously added the "fact" that if you use the frequency that Google returns if you search for "once in a blue moon" you get a different number of years (also specified with lots and lots of digits). I removed all this and simply stated that the blue moon occurs about once every 2.7154 years -- these are the digits up to which  the frequency provided by Google (1.16699016 × $$10^{-8}$$ Hz) and the result of the calculation synodic month / (vernal equinox year - 12 * synodic month) match. (The synodic month is the period of the moon's phases, and the vernal equinox year is the year that the major calendars try to track.) If you add any digits beyond this, please provide a source. Joriki (talk) 19:22, 12 April 2009 (UTC)


 * Very good idea! We're trying to help people understand not confuse them more, right? Greg (talk) 07:48, 22 April 2009 (UTC)


 * So I removed the confusing decimal fraction and replaced it with what really matters, i.e. that this happens 7 times in 19 years (19/7 = 2.714285......) -- Tom Peters (talk) 15:09, 31 December 2009 (UTC)

Contradictory and Incoherent
This article is contradictory and incoherent. The most obvious contradiction is that the definition given in the intro is contradicted later in the article.--Jack Upland (talk) 00:37, 28 December 2009 (UTC)


 * Please elaborate. I see no contradiction.  The introduction states that the norm is 12 Full Moons in a calendar year, one in each calendar month.  Any 13th Full Moon is the blue one.  Which one is called the blue one depends on the definition you use.  All that follows in the article is consistent with this. -- Tom Peters (talk) 15:06, 31 December 2009 (UTC)

Well, at the very least, it's incoherent. The introduction should say there are a number of interpretations of the term "blue moon". These are: These "definitions" are mutually contradictory, and to dump them in the introduction and the body of the article like this makes for a very incoherent and misleading article.--Jack Upland (talk) 09:23, 12 January 2010 (UTC)
 * A proverbially rare or unlikely event.(Well attested.)
 * A moon that actually appears blue.(Well, obviously.)
 * An extra moon in a season as defined by the Farmers Almanac. (An arbitrary definition. And, by the way, just because an American said something 70 years ago doesn't make it traditional.)
 * An extra moon in a month. (Another arbitrary definition. Attested by some dude.)
 * A moon allegedly involved in the calculation of Easter and allegedly described by English clergy as a "belewe" moon. (Complete and unsubstantiated nonsense.)


 * No, they are not contradictory. The lemma is about the thing called a "Blue Moon", not exclusively just the English saying "once in a blue Moon".  The term "Blue Moon" has been used for several slightly different events, as is well documented in all the refs given.  Apart from a literal meaning, the common factor of these events is that it is an irregular 13th Full Moon, as stated in the first sentence.  But it is well documented that there have been different interpretations and conventions which Full Moon is to be considered the odd one.  Each of the quoted meanings has been used in print at some time; whether you consider it written by "just some dude" is irrelevant, at best you could claim lack of notoriaty.  The earliest known usage is in an (anti-)clerical context.  The supposed meaning of "treacherous" and the Easter computation is an interpretation, and it remains speculative - unsubstantiated if you like - but is not complete nonsense.  It does in fact explain the origin and meaning of the phrase, and its time of origin during the protestant reformation and before the Gregorian calendar reform when the ecclesiastic calendar was a mess, adds to the credibility of the hypothesis.  Anyway, it is an explanation given in the external references.  The "Blue Moon" has been widely investigated and such events have been increasingly publishized in the recent past - see the press coverage of the latest occurrence - so the various meanings are worthy of mention here. Tom Peters (talk) 22:09, 12 January 2010 (UTC)


 * The term "belewe" meaning "betray" is English. Hence the article posits that the Easter computus was an English affair, which is nonsense.  It is also nonsense to say that Easter was calculated on an ad hoc year-to-year basis by the observation of the moon by "clergy".
 * The Julian Calendar was not a "mess". It had served Europe well for centuries and continues to be used by the Orthodox Church.  The Gregorian Calendar is only a minor modification, differing by one day per century.  As the Gregorian adjustment was sponsored by the Pope, Protestants actually resisted it.  Protestant England stayed with the old calendar for some time.  It is therefore nonsense to state that attacking the Julian Calendar was anti-clerical.--Jack Upland (talk) 19:05, 14 January 2010 (UTC)
 * Jack, I do not understand what you base these assertions on. The article does not say nor insinuates that the computus was an exclusively English affair.  It says that clergy used a traditional computus to determine Easter day, and the problem is that at the time that date was in obvious contradiction with the intended date of the first Sunday after the first full moon of spring; at which the English clergy might have called the true first full moon of spring a "belewe" moon.  Clergy elsewhere would have used a different word, but this article is about the meaning and origin of the English expression.
 * The article does not say nor insinuate that the clergy computed Easter ad hoc (it explicitly states that they used the traditional computus), it says that anyone else following the informal definition could see that the computus was frequently wrong.
 * The Julian calendar was a mess and that was well known at the time - this was fruitlessly discussed during the Council of Trent (1545..1563). "Julian calendar" more properly is the ecclestiastic calendar, which has both a solar and a lunar calendar, exactly for the purpose of computing the date of Easter.  The original Julian solar calendar had accumulated an error of not 1 day, but (at least) 10 days for the seasons: the aequinox fell at 10 or 11 March in the Julian calendar, instead of 21 March as the computus assumed, being calibrated at the time of the council of Nikaia (325 AD).  The Gregorian reform made a one-time leap of 10 days to put the aequinox back at 21 March, and changed the intercalation rule to prevent the seasons from drifting through the calendar again.
 * Moreover, the Gregorian reform also thoroughly reformed the computus of Easter and therefor also the lunar calendar. This was the main reason for the reform, see e.g. the proceedings of the Vatican conference on the 400th anniversary of the reform: http://articles.adsabs.harvard.edu//full/book/grc../1983//0000001,001.html, esp. the article of J.D.North.  The Gregorian reform was not universally rejected by protestants, e.g. adapted early in the Netherlands and Germany.  The first appearance of "belewe moon" is in an anti-clerical pamphlet, so that is relevant.  That later the English state and church did not accept the Gregorian reform is another issue and not so relevant; the Anglican church was catholic in all but name, and these diversions appear more politically than religiously inspired.

Just look at the discussion of the computus in Wikipedia. Does it mention the "betrayer moon" or anything like it? No, no, no. Other than that I would only say I stand my all my statements as they are factual and logical.--Jack Upland (talk) 01:46, 23 January 2010 (UTC)
 * Troll alert. Just look at his personal page. Tom Peters (talk) 15:55, 23 January 2010 (UTC)

For your information, my personal page was vandalised by other people and I haven't bothered to change it. You seem to have a dogmatic attachment to your own opinions. You don't seem to accept that other people can have legitimate disagreements and can legitimately demand evidence for the assertions in supposedly encyclopedic articles.--Jack Upland (talk) 22:01, 23 January 2010 (UTC)


 * We have three indications at the moment of "blue moon" used to mean an infrequent event:
 * In Jack's list above: A proverbially rare or unlikely event.(Well attested.)
 * In the article at the moment: A "blue moon" is also used colloquially to mean "a rare event"
 * At the reference: The phrase blue moon has become a metaphor for a rare event.
 * but what actual examples has anybody come across? My point is that these statements all indicate that the infrequent event is described as being a blue moon, which I've never come across, as opposed to merely happening once in a blue moon. -- Smjg (talk) 18:41, 6 April 2010 (UTC)


 * It is not proper to make all these changes to the article that so many have worked on without discussing it first on the talk page. I can't make heads or tails out of what you have done or are concerned about.  Can someone please revert this editor's changes?  I would do it myself if I had more experience, but I don't want to make a mistake and make it worse than it is...if that would be possible. :(  Gandydancer (talk) 01:40, 7 April 2010 (UTC)
 * Revert which editor's which changes? -- Smjg (talk) 11:06, 22 April 2010 (UTC)

Jack Upland's objection seems sound to me. For instance, the article begins by giving the recent definition, said to be based on an error in Sky and Telescope a mere 40 or 60 years ago (it wasn't consistent), and buries what it seems to say is the original definition in the body of the article. I am tempted to simply move the "original" definition to the introduction with the "new" definition so at least anyone in a hurry won't get a wrong impression. Best would be if someone with scholarly knowledge helps out. Zaslav (talk) 05:35, 21 August 2013 (UTC)

Photos
This article needs a photograph --Melly42 (talk) 23:59, 31 December 2009 (UTC)

Night of love section
I'd like to see a reference for this if it to be included. If no reference is provided, I'd like to delete it. Gandydancer (talk) 17:32, 14 January 2010 (UTC)
 * I second that. I think it is a fantasy. Tom Peters (talk) 18:19, 15 January 2010 (UTC)


 * You are being more generous than I when you ask for a ref (referring to the two article citations you added). I know a fair amount about myths and this sounds like some teenage fantasy. How about getting rid of it till it's referenced?  It's just plain dopey and makes the article look bad.Gandydancer (talk) 18:33, 15 January 2010 (UTC)


 * No reference yet. Removed till a reference is furnished. Gandydancer (talk) 17:03, 17 January 2010 (UTC)


 * Section put back without reference or comment. Removed again. Gandydancer (talk) 15:47, 19 January 2010 (UTC)

question
Does the blue moon have anything to do with the expression out of the blue? Just wondering... :) – Alensha   talk  20:22, 9 February 2010 (UTC)

Luck
Blue Moon's are assaociated with bad luck also aren't they?

Like the phrase "Born under a Blue Moon", implying that the person/thing is cursed with Bad luck or something. —Preceding unsigned comment added by UFOash (talk • contribs) 19:33, 18 November 2010 (UTC)


 * Plurals are not formed with apostrophes. The Real Walrus (talk) 20:10, 19 November 2010 (UTC)

Eclipse of a Blue Moon
Does anybody know when the last total eclipse of a blue moon was? I realize there was a partial just last year, on Dec 31 2009. If this information is available I think it would make an interesting addition to the article. Nibios (talk) 18:21, 21 December 2010 (UTC)
 * Sorry I took so long to answer. The last total eclipse of a blue moon under the Gregorian calendar definition was the 30 December 1982 lunar eclipse, visible throughout eastern Asia and the Pacific Ocean west of the International Date Line. The eclipse was also visible in the eastern Pacific Ocean, but it not as a blue moon there because the preceding full moon was the blue moon of 30 November rather than being on 1 December in that region. Such eclipses are very rare and frequently cover only limited regions of the globe because of the nature of the calendar. The next total eclipse of a blue moon will be the 30–31 July 2102 lunar eclipse, visible throughout eastern Asia and most of the Pacific Ocean. The eclipse will also be visible in the central and eastern portions of Europe and Africa but not as a blue moon there because the preceding full moon will be the blue moon of 30 June rather than being on 1 July in that region.


 * However, if we use the Maine Farmers' Almanac definition of "blue moon," such total eclipses of blue moons are extremely rare. In this case the last such was the 23–24 August 1877 lunar eclipse. The next will be over two hundred years later, the 21–22 November 2105 lunar eclipse. Under this definition, such blue-moon total eclipses are visible anywhere the full moon can be seen, and are not dependent on either the type of calendar used or the time zone.


 * Regardless of which definition of blue moon is used, most of us will not live to see the next total eclipse of a blue moon. — Glenn L (talk) 07:24, 9 December 2012 (UTC)

Two full moons in one month
I've always been taught that a blue moon is the second full moon in a single month. AmericanLeMans (talk) 02:22, 18 January 2011 (UTC)


 * This is also used in http://oeis.org/A125680 and http://www.obliquity.com/cgi-bin/bluemoon.cgi and menioned in an earlier comment above. &mdash; MFH:Talk 21:07, 31 December 2011 (UTC)


 * In the July 1943 issue of "Sky & Telescope magazine columnist Lawrence J. Lafleur made reference to the term "Blue Moon." Being that there are 13 full moons during a calendar year, there will be 4 full moons during one of the 4 quarters. In generic terms, using summer for example, the full moons are called the "Early Summer Moon"; "Midsummer Moon"; and "Late Summer Moon". According to the 1937 edition of the defunct Maine Farmer's Almanac when the 4th full moon occurs during that season the Blue Moon is the third full moon. The second full moon would remain the mid season moon, and the 4th would remain the late season moon. In 1980 Deborah Byrd of Earth & Sky stated, in error, that the Blue Moon was the second full moon during a solar calendar month. She neglected to explain that she was describing one specific occurrence of one full moon during one specific month. The rule Ms. Byrd used was from the 1937 almanac, but in that one month, in that one season, in that one year the Blue Moon did fall at the end of that particular month. Her brief explanation gave the impression of a new rule, which it was not. Because of the lack of correction and current popularity, both rules can be used accurately. MR2David (talk) 08:06, 19 August 2013 (UTC)

Smurfs
Not that it should be added to the article, but this Wikipedia article (and a photo "blue moon.jpg") feature fairly prominently in the new The Smurfs movie. Bookcats (talk) 01:45, 30 July 2011 (UTC)

Purkinje Effect
It could also be that the notion of a blue moon is related to the Purkinje effect. The effect is described as:

"Peak luminance sensitivity of the human eye to shift toward the *blue* end of the color spectrum at low illumination levels." http://en.wikipedia.org/wiki/Purkinje_effect

Film production sometimes uses dark blue filters to simulate night filming. The result looks natural because of the Purkinje effect I guess.

Janburse (talk) 17:18, 16 August 2011 (UTC)

"Real" blue moon eclipse
The French version of this article claims that there is another phenomenon called "Blue Moon" in which the moon actually becomes blue during an eclipse under extremely rare circumstances (the Earth being extremely cold would send back blue light to the moon instead of the more common infrared that turn the moon to red). It also claims that Confucius mentions one such moon as "icy looking". Does anyone know about this? I couldn't find any other information on the web about it, and it is also not mentioned in other languages on Wikipedia (at least not in the German, Spanish, Italian, Russian and Portugese ones). It would be interesting to get more information from a real historian/scientist on this point. — Preceding unsigned comment added by 193.9.13.133 (talk) 13:12, 30 August 2012 (UTC)
 * Actually a bluish edge of the umbra during a total lunar eclipse is rather common. It is caused by absorption of red light by Earth's ozone layer for some of the light rays that pass through the Earth's atmosphere on the way to the moon. — Preceding unsigned comment added by 67.6.130.136 (talk) 23:27, 24 January 2015 (UTC)

farmers almanac
It's important to note that there is more than one farmers almanac and we shouldn't confuse them. The one that started the confusion in the 40's with a Sky and Telescope writer is the "Maine Farmers Almanac". That should not be confused with either the "Farmers Almanac" or the "Old Farmers Almanac" which are different publications.--RadioFan (talk) 22:16, 31 August 2012 (UTC)


 * I have corrected references to the Farmers' Almanac to Maine Farmers' Almanac (further to your own edit). In fact, I had begun making the changes before seeing your post here.  It's amusing that two people should notice this confusion almost simultaneously (though, of course, it's no surprise that the article should be getting an unusual amount of attention on this date).  The article must have been in this confused state for some time, despite the cited Farmers' Almanac article pointing out that the Maine Farmers' Almanac is "(no relation to this Farmers' Almanac, published in Lewiston, Maine)". Butsuri (talk) 23:55, 31 August 2012 (UTC)

Suspect etymology
I have done some searching (Middle English, Old English, Anglo-Saxon, Scots), and can't find a pre-20th century etymology that gives "belewe" as an origin for "blue". The closest is "blæwe". Nor can I find "belewe" as having the meaning "betrayer". The closest is "bewray". I can't find the quote "If they say the moon is belewe [blue] / We must believe that it is true." in a pre-twentieth century source. The reference [3] cites the first part of the quote "Rede me and be not wrothe", but I don't find the alleged second part "If they say the moon is belewe [blue] / We must believe that it is true." 96.54.42.226 (talk) 03:50, 24 September 2012 (UTC)


 * I found a few sites that say the word/phrase was used to mock the church.
 * One theory claims that the medieval church, which often announced the dates of religious celebrations on the basis of positions of the Moon (since the largely illiterate population of the time made little use of printed calendars), occasionally had to dismiss an extra moon before the beginning of Lent. It did so by labelling that moon a "belewe" Moon - a word meaning blue, but also "betrayer," or false. A medieval blue Moon was therefore a "false" Moon which occasionally disrupted the cycle of Lent. The often-quoted Middle English rhyme that "if they say the moon is belewe [blue], we must believe that it is true," a sarcastic commentary on the authority of the Church, is therefore probably intended as a play on words (the clergy say the moon is false or "blue," when obviously it is not blue at all). Gandydancer (talk) 11:38, 24 September 2012 (UTC)
 * If "Sites" means web sites, they are clearly of 20th or 21st century origin. The web can unfortunately be an echo chamber of recently fabricated "explanations" of old sayings. Can you find authentic mediaeval references? The date of Easter was determined by a complex formula, not by local clerics determining it to be so by counting full moons.96.54.42.226 (talk) 04:58, 5 November 2012 (UTC)
 * Actually, Easter is based on the calculation of clerics. The holiday has been celebrated on the church calendar and counted on the first Sunday after the first full moon after the Spring Equinox. From that formula, if you count forward 49 days, you will find that you are at the Jewish Sabbath of Pentecost. MR2David (talk) 08:22, 19 August 2013 (UTC)

The objection by 96.54.42.226 has not been answered. Does someone have enough knowledge to give an answer? Zaslav (talk) 05:26, 21 August 2013 (UTC)


 * I have looked and found nothing. You might find a book with some info...  Gandydancer (talk) 13:39, 21 August 2013 (UTC)

my recent delete...
Sorry re my recent knee jerk delete in the lead. So many times people have tried to edit the seasonal blue moon out that I have grown careless and just assume they are wrong. The edit was an improvement. Sorry... Gandydancer (talk) 13:36, 21 August 2013 (UTC)

Incorrect value
"According to Google Calculator, "once in a blue moon" is equal to 1.16699016 × 10-8 hertz." — Preceding unsigned comment added by 87.171.11.242 (talk • contribs) 10:46, 8 February 2014 UTC
 * This value is wrong by more than 10 percent!
 * Duration of a synodic period of the moon in days: T = 29.53058912
 * We have 4 months with 30 days and 7 months with 31 days. Other months are shorter than T.
 * Probability of a Blue Moon within a year: H = 4*(30/T - 1) + 7*(31/T - 1) = 0.411895599
 * Average Distance between Blue Moons: Y = 1/H = 2.427799675 years (as frequency: 1.305246263 × 10-8 hertz)
 * This value is identically for the Gregorian calendar as for the Julian calendar (and for all calendars with four 30-days months, seven 31-days months and months which are always shorter than T).
 * WP:OR. EvergreenFir (talk) 04:14, 11 February 2014 (UTC)
 * See the explanation which is also a synthesis - a good reference about frequency or explanation about how Google derived its figure would help.  If the Metonic cycle were perfect, then it looks like 7 occurrences in 19 years which is within 0.05% of Google in a Julian calendar. --Cedderstk 12:49, 3 August 2015 (UTC)

blue moon
Can someone tell me why it called a blue moon? Liana05omg (talk) 02:37, 19 February 2016 (UTC)
 * Have a look at the "Origin of the term" section in the article. —Bruce1eetalk 04:51, 19 February 2016 (UTC)

Church Dates of Seasonal Blue Moons
I find it interesting that the church calculates a rather complex array of months where they need to insert an extra month (moon month) to make everything else fit. I am deleting my earlier text asking where it all fit with blue moons.

"The extra months commenced on 3 December (year 2), 2 September (year 5), 6 March (year 8), 4 December (year 10), 2 November (year 13), 2 August (year 16), and 5 March (year 19)" (from the Computus entry).

All their observations which came to the 19 year formula and placing of moons had to originally come from observances of moon timings and winter/summer solstices, approximated into the computus.

Now to work out what the church called their extra moons Greg (talk) 05:36, 24 May 2017 (UTC)

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Dates in 2018
How can a blue moon be on the first of the month ever? — Preceding unsigned comment added by 157.248.100.53 (talk) 22:35, 27 September 2018 (UTC) Surely these dates are incorrect? 2018: January 2 and 31, only in time zones west of UTC+11. 2018: March 2 and 31, only in time zones west of UTC+12. — Preceding unsigned comment added by 124.169.112.121 (talk) 04:16, 31 January 2018 (UTC)

'Betrayer moon'
There have been at least two rather unsatisfactory discussions above on this topic (here and here), going back at least as far as 2008. Until I amended it just now, our article had a relatively lengthy but deeply misleading paragraph on the subject, seemingly backed by 3 reliable sources. In fact two of these sources (here and here) seemingly made no mention of Blue Moon, let alone Betrayer Moon, and the third (here) simply repeated a speculation without mentioning that its originator had already admitted it was completely wrong. Our article then added much that was not in that source, as well as another related deeply implausible unsourced speculation later in the section (Old English disappeared in the 12th century, so there is no reason to think it likely that anti-clerical writers around 1528 knew anything about Old English words, still less that they would expect their readers to know such words). I have tried to fix all this as best I can, tho others may well do a better job than I have. I have also considered removing all mention of the speculation, but that would leave a fiction partly created by us circulating out there uncorrected, without any real attempt by us to undo the harm that we had done by presenting the correct facts to the readers whom we had previously helped to mislead. (Indeed a part of me would like to say in the article that Wikipedia had contributed to the problem, but in the past I've found that such admissions tend to get at least one such admission eventually got removed for various reasons, possibly rightly so). Tlhslobus (talk) 11:06, 28 July 2018 (UTC)

Physical blue moon.
This article is very biased towards American usage. I expect my edits to be reverted by Americans, but the contents of the article constitute the third definition in the OED Third Edition updated March 2013. Can we not have a less biased article that gives equal weight to the OED's definition 1: "A moon (real, depicted, or imagined) that appears blue. On rare occasions the moon can appear distinctly blue owing to the presence of smoke or dust particles in the atmosphere"? Dbfirs 07:49, 9 July 2019 (UTC)


 * I reverted you but it has nothing to do with being an American. A few years back I researched this issue extensively and as best as I can understand it is correct as it reads.  Can you offer RS to back up your assertions?  Gandydancer (talk) 16:08, 9 July 2019 (UTC)


 * Only the Oxford English Dictionary. The article presents a very American viewpoint, but since most on-line references are recent American sources, it is difficult to present a counter-argument.  I'll do some research myself.  I'm pleased to see that the false "betrayer" folk etymology has been debunked.   Db<i style="color: #4fc;">f</i><i style="color: #6f6;">i</i><i style="color: #4e4;">r</i><i style="color: #4a4">s</i>  17:43, 9 July 2019 (UTC)


 * The best explanation that I have found so far of how the meaning developed in America is on pages 118 to 120 of How the Ray Gun Got Its Zap: Odd Excursions Into Optics by Stephen R Wilk here on Google Books.  <i style="color: blue;">D</i><i style="color: #0cf;">b</i><i style="color: #4fc;">f</i><i style="color: #6f6;">i</i><i style="color: #4e4;">r</i><i style="color: #4a4">s</i>  18:15, 9 July 2019 (UTC)

Citation required?
Under books there is a citation required for the statement "Note that if two full moons fall within the same astrological sign they will fall in different calendar months, and vice versa." Is there a need to find a source that states the astrological signs change about the 21st of each month and the lunar cycle is ~28 days? The offset between the calendar month and the astrological cycle can never include 2 full moons. Brian (Shadowfoot) (talk) 11:25, 17 August 2019 (UTC)

Actual Usage Quotes and tidy up
Putting this link here for later. The article needs to have the uncited speculation stripped out and some actual references put in. It seems at the very least that evidence of the proverb usage predates the evidence of the calendar usage... So three sections: Proverb Astronomy Calendar

https://wordhistories.net/2017/06/21/once-in-a-blue-moon-origin/

Jmackaerospace (talk) 02:31, 3 October 2020 (UTC)

Section removed
I removed the Popular culture section because none of the topics mentioned had anything to do with the scientific term blue moon. I was reverted saying I needed to allow time for improvements. It was tagged over a year ago--that seems to be enough time for needed work to be done. For example in the song "Blue Moon of Kentucky" with Monroe singing, "Blue moon of Kentucky keep on shinning, shine on the one whose gone and left me blue"--what does that have to do with the scientific term? Sectionworker (talk) 16:42, 20 March 2022 (UTC)
 * I've waited for over a week and nobody has improved the article or even replied with information on why the section should be kept.  I will again remove it.  Sectionworker (talk) 04:00, 29 March 2022 (UTC)

This page needs a lot of work for a real lexicographer
The English use of"in a Blue Moon", seems to date from no later than 1821, Real Life in London by Pierce Egan.

See https://www.theidioms.com/once-in-a-blue-moon/ cited in this article.

So is unlikely to have anything to do with a provincial journal, first published in 1819. 86.161.210.123 (talk) 00:07, 3 September 2023 (UTC)

Oxford English Dictionary
The OED has an extensive entry for "blue moon", and I've added this at the start of the article. A lot of what follows in the article is now repetitive and redundant, in some cases inaccurate, and needs to be shortened or removed. Cheeselymoon (talk) 14:01, 3 May 2024 (UTC)


 * I've done a lot of re-ordering of material and removal of repetition, but the "Calendrical use" section still has a lot of redundancy and could do with tidying up. Cheeselymoon (talk) 16:19, 8 May 2024 (UTC)
 * I've put new material in the "Calendrical use" section. The "Calculation" sub-section needs attention. There needs to be clarity about which rule is being referred to in any calculation, i.e. Maine 1937, Maine using different (e.g. astronomical) seasonal boundaries, Pruett or "other". Cheeselymoon (talk) 21:47, 10 May 2024 (UTC)