Talk:Date of Easter

@Tom Peters: Tom, what do you think? I added the following paragraph:

One may wonder whether the pattern of dates of Easter repeats. As can be verified in a table of the dates, the dates from 1948 to 2047 are the same as for those 152 years later (2100 to 2199). This period of 152 years is one day short of two Calippic cycles, and is a whole number of weeks. Also the dates for 1800 to 1899 are the same as those for 152 years later (1952 to 2051) in all but 11 cases. The epacts differ by 1, as do the dates of the ecclesiastical 14th of Nisan, but usually the next Sunday falls on the same date. It is possible to have the same dates for the 14th of Nisan and on the same day of the week for other intervals, but since the golden number is not the same, this situation lasts for less than 19 years at a time. For example, the 100-year period 1980-2079 is almost repeated 220 years later (2200-2299), but with six cases that don't agree. An interval of 18,000 years achieves this in some cases

Footnote (which I can't seem to put here in the talk page): It is easy to verify that this occurs if the interval contains 58 lunar corrections and the golden number of the first of the two years in question is less than 13, or if there are 57 lunar corrections and the first golden number is greater than 12. In either case, these cancel out the 135 solar corrections.

and is also a whole number of 400-year Gregorian cycles, but again the golden number will be different, so the pattern does not repeat exactly.

Five minutes later Jc3s5h reverted it, saying that it's a "wall of text" that doesn't answer the question I asked at the beginning -- whether the pattern repeats, and he says it repeats in 5.7 million years. Well of course, we all know that. But does that justify reverting my edit? The question I mean is whether the pattern repeats for a while, like a century, and the answer is yes. I think it's quite interesting, and should be in the article. Eric Kvaalen (talk) 19:25, 10 September 2023 (UTC)

I was going to revert it and Jc3s5h beat me to it by minutes. It reads far too much like a blog post, beginning with "One may wonder whether the pattern of dates of Easter repeats" which is exceedingly unecyclopedic. It was also too far too long for the thoughts expressed. Arguably it works better as a talk page post here to open a discussion on whether/how to express your thoughts. DeCausa (talk) 19:33, 10 September 2023 (UTC)

So why don't you modify the wording instead of deleting the whole thing?? I wish you people would stop complaining every time someone puts something interesting into an article. Nobody is forcing you to read it, after all! Other people might want to read it. Eric Kvaalen (talk) 20:34, 10 September 2023 (UTC)

I didn't delete it. But if I had I would reject your point because it's not my job to correct your failings. Why should I put effort into dragging out some sort of value in your edit when I can't see any? It's not interesting and it shouldn't be in the article. DeCausa (talk) 20:37, 10 September 2023 (UTC)

You and Jc3s5h act like Caesar watching the gladiators, and giving a thumbs up or thumbs down. Who made you the judges? I think it's very interesting that the pattern repeats exactly or almost exactly over periods of 100 years, at certain intervals. Another case I didn't put is that 1700-1747 is exactly the same as 1852-1899. One would think that people interested in Easter would show a bit of Christian charity. Eric Kvaalen (talk) 09:01, 11 September 2023 (UTC)

In that case, we may as well have a triumvirate. I'd have reverted it too, per WP:TRIVIA. It is a mathematical artefact of no significance. A form of pareidolia. --𝕁𝕄𝔽 (talk) 09:22, 11 September 2023 (UTC) revised 09:27, 11 September 2023 (UTC)

I love a thread where pareidolia is an issue. :) DeCausa (talk) 10:00, 11 September 2023 (UTC)

I think the issue is interesting enough that if a good source (other than the dates themselves) can be found, and if it can be stated briefly and clearly, it may be relevant for the article -- but it is up to user:Eric Kvaalen or others who want to include it to demonstrate that. In the Gregorian calendar there is a period-4 stemming from leap years and a period-7 stemming from days of the week, combining into a period-28 (not related to churches, Easter or holidays) so that e.g. from 1901 to 2099, the calendar for any two years separated by a multiple of 28 years is the same (all Mondays fall on the same dates, etc.) - but the "missing" leap years in 1700, 1800, 1900, 2100, 2200 ect. spoil the fun. Incidentally, the true period-400 in the leap years coincide with a whole number of weeks (400*365 + 100 - 3 = 146097 days = 20871 weeks), so there is a true, perpetual period-400 in the Gregorian calendar. -- Is that relevant here? No, but if similar neat patterns could be descirbed for dates of Easter - and sourced - including it would be fine. Nø (talk) 12:37, 11 September 2023 (UTC)

@JMF and Nø: Well, as explained in our article, the only true period for the Easter dates is 5,700,000 years. I disagree that what I wrote is just a "mathematical artefact of no significance". The reason what I wrote works is that 152 years is a day short of two Calippic cycles, which means that the phase of the moon is more or less the same, and the fact that a Calippic cycle has four days more than a whole number of weeks means that two Calippic cycles minus 1 day is a whole number of weeks. So whenever the 152 years spans one year like 1800 where the Gregorian calendar drops a leap year, and there's also a lunar correction, then you get periods that follow exactly the same pattern, for 48 or 100 years. If the 152 years does not span a year like 1800 (for instance going from 1900 to 2052), then we have exactly two Calippic cycles, so the day of the week is off by 1. That gives periods where the pattern is almost the same. All this is of interest to mathematically minded people like me. I have no idea where to find a reference for all this, but why do we need a reference for something that can be easily checked? We don't need a reference in order to say that it's an interesting question, after all. I suggest that those of you who don't find it interesting stop reading it and go find something else to do in life rather than deleting the work of other people. Eric Kvaalen (talk) 16:20, 11 September 2023 (UTC)

Eric Kvaalen asked "...but why do we need a reference for something that can be easily checked?" If a numerical curiosity is mentioned in several well-regarded sources, that hints that it's worth including in our article. If no reliable sources felt it was worth mentioning, it probably isn't worth mentioning. Jc3s5h (talk) 16:31, 11 September 2023 (UTC)

I suggest that those of you who don't find it interesting stop reading it and go find something else to do That could be addressed to our readership. This article isn't a personal blog existing for your self-indulgence. DeCausa (talk) 19:27, 11 September 2023 (UTC)

I hope it's clear from what I wrote yesterday that this is not a case of pareidolia. I have a question for Caligula, Claudius, and Nero: You say what I wrote is not interesting, and I suppose you are concerned for the disk space of Wikimedia. What if I find three μαρτῠ́ρους who will attest to finding that it is interesting? Is it still you who get to decide? Eric Kvaalen (talk) 07:09, 12 September 2023 (UTC)

You need to read WP:CONSENSUS (although "find" sounds like you also need to read WP:CANVASS). And don't you mean Caesar, Pompey and Crassus? DeCausa (talk) 07:17, 12 September 2023 (UTC)

And you have to show a reliable source that considers this factoid to have any significance, specifically in respect of calculation of the date of Easter. --𝕁𝕄𝔽 (talk) 15:04, 12 September 2023 (UTC)

It's Catch 22. There are three Caesars, or shall I call them watchful dragons, guarding this page to prevent any changes they don't agree with. If they revert you, you're stuck. You can't revert back or you get warnings of "edit wars". You can't ask someone else, or you get accused of canvasing. I have three friends who I think would agree with me that what I wrote was interesting, but I'm told that it doesn't matter. What the Caesars want is what happens. I'm told that I have to find a "reliable source" to say that it's interesting! Just another way of preserving the statum quo ante. Now I'll probably get a warning for arguing. Eric Kvaalen (talk) 06:54, 20 September 2023 (UTC)

No warning, but I am surprised that after 18 years and 10k edits on Wikipedia (I just checked) these very basic policy principles seem to be news to you. Do you really not know about WP:CONSENSUS, WP:CANVASS, WP:V and WP:DUE? DeCausa (talk) 07:00, 20 September 2023 (UTC)

Yes, I know the cards are stacked against me. Eric Kvaalen (talk) 10:02, 20 September 2023 (UTC)

Eric, no, the cards are not stacked against you, or to be more precise, they are stacked against any editor who tries to add original research or trivia. Let me repeat: all you need to do is to find "a reliable source that considers this factoid to have any significance, specifically in respect of calculation of the date of Easter". Consensus (or lack thereof) does not trump reliable sources. --𝕁𝕄𝔽 (talk) 10:18, 20 September 2023 (UTC)

Well, I don't actually agree with that - WP:ONUS says specifically otherwise. DeCausa (talk) 11:28, 20 September 2023 (UTC)

True but as it is a (very) hypothetical question, I didn't consider it necessary to qualify my response with details of the more advanced aspects of source quality and preponderance of expert opinion. We are nowhere near that stage; right now, we have no sources whatever that attach any significance to Eric's mathematical coincidence. --𝕁𝕄𝔽 (talk) 12:08, 20 September 2023 (UTC)

But to be unambiguously clear: if Eric succeeds in producing citations that meet my test, I will change my !vote from 'oppose' to 'support'. "When the facts change, I change my mind. What do you do, sir?"—Paul Samuelson. --𝕁𝕄𝔽 (talk) 15:50, 20 September 2023 (UTC)

There were three issues with this edit, only one of which was lack of sourcing. The second is whether it's worth making the point. I could be swayed on that by sourcing but it would take more than one rogue source to do that. But the third is the meandering blog-style WP:WALLOFTEXT would have to be converted into encyclopedic language which was considerably shorter (and which certainly doesn't begin with "One may wonder..."). DeCausa (talk) 20:34, 20 September 2023 (UTC)

If it hasn't materialised by now, it isn't going to. My point was about the general principle. --𝕁𝕄𝔽 (talk) 22:17, 20 September 2023 (UTC)

I made a contribution to this article earlier this year replacing Gauss's algorithm, which was described in a table, with pseudocode.

User @Crissov has undone the edit "because the table more accurately reflects Gauss's notation". The discussion, I suppose, is: Does that matter? Why? I'm sure there are countless aspects of the notations used 200 years ago that we have long since abandoned. Why preserve this one? Isn't it more important to convey the information clearly?

And then there is the fact that the article links to a beautiful scan of the original work by Gauss. Citation number 58. You can see for yourself there, there is no table of any sort. He described the algorithm longhand. You can see right there in Seite 2, page 122, The three paragraphs with the roman numerals which outline the operations. If the intent is "preservation" let's just translate his work directly! Should be something roughly like "Divide the number of the year for which you want to calculate Easter by 19, by 4 and by 7..." Introscopia (talk) 19:38, 10 May 2025 (UTC)

Does anybody have an RS for the date in the Coptic calendar? I've just cleared out load of waffle, leaving nothing behind. 𝕁𝕄𝔽 (talk) 15:31, 12 July 2025 (UTC)

if it says "the same as Greek Orthodox", that's good enough. 𝕁𝕄𝔽 (talk) 21:54, 12 July 2025 (UTC)

I always understood it to be the same as Orthodox Easter but with the Julian calendar date expressed as a Coptic calendar date: 22 March (Julian) = 26 Paremhat, ..., 25 April (Julian) = 30 Parmouti.

The standard source on the Coptic calendar is Marius Chaîne, La chronologie des temps chrétiens de l’Égypte et de l’Éthiopie (Paris, 1925) and there is a discussion in Calendrical Calculations, chapter 4. AstroLynx (talk) 02:41, 13 July 2025 (UTC)

Another source mentioned in CC is Cérès Wissa Wassef, Pratiques rituelles et alimentaires des Coptes (Cairo, 1971), chapters II & V. AstroLynx (talk) 09:29, 13 July 2025 (UTC)

Drat, of course. I should have thought of Calendrical Calculations. Sorry. 𝕁𝕄𝔽 (talk) 10:20, 13 July 2025 (UTC)

I remarked a few years ago that we haven't got a section on the Orthodox calculations. If someone with a rather better attention to detail than I have would like to take on the task, pp 115–116 of Calendrical calculations has chapter and verse. 𝕁𝕄𝔽 (talk) 15:14, 13 July 2025 (UTC)

Julian Easter is the same as Orthodox Easter (for most of the Orthodox churches). It is covered by the Meeus Julian algorithm in the article. What kind of additional coverage did you have in mind?

I have been doing some work to clean up Ecclesiastical full moon.

The excerise has opened up an intriguing question: does the ecclesiastic lunar calendar have a formal name? (The ecclesiastic calendar as commonly understood is the a schedule of saints' days and movable feasts for a particular solar year. In this case I refer to a lunar year of twelve months alternating 29 or 30 days.) The reason I ask is that the only example we give for a true lunar calendar is the Lunar Hijri one yet for many readers of en.wp, the Christian one should be more familiar. But we don't seem to have an article about it - it is mentioned almost in passing at Epact, Metonic cycle and Golden number (time), all of which seems to put cart before horse. Or have I missed something really obvious? 𝕁𝕄𝔽 (talk) 14:23, 10 March 2026 (UTC)

The lunar calendar used by Western Christian churches for 200 years or more is part of the Gregorian calendar. It is mentioned in passing or in footnotes in the "Gregorian calendar" article. The main Wikipedia description seems to be the "Gregorian reform of the computus" section of the "Date of Easter" article.

It is a lunar calendar in the sense that it provides rules that allows one to know the dates of the various lunar phases with considerable accuracy, compared to actual observations of the Moon. But it is not a lunar calendar in the sense of being used to regulate daily life. For example, one would not use the lunar calculations of the Gregorian calendar to figure out when to pay one's rent. Jc3s5h (talk) 18:41, 11 March 2026 (UTC)

Yes, re-reading the Epact article reminded me that its recalculation was an essential hurdle that had to be cleared for the Gregorian reform to even happen. But to call it "the Gregorian lunar calendar" seems very dubious to me as it is a practice that long predates Gregory (albeit that it was rebased (sic?) in the same reform). And we do have religious calendars, so its use to schedule rent days is not a definitive criterion.

What a pity. 𝕁𝕄𝔽 (talk) 19:54, 11 March 2026 (UTC)