Talk:Date of Easter

Drift in ecclesiastical full moon

Per WP:TPO, closing section created by IP sockpuppet of banned User:Vote (X) for Change
The following discussion has been closed. Please do not modify it.
It would be more helpful to tweak the wording, rather than nuke the section entirely. The value of delta T over 2,000 years has reached about 3 1/2 hours. The shift in the time of full moon over the same period is much the same. So the one cancels the other out. 156.61.250.250 (talk) 10:44, 14 May 2015 (UTC) The deleted section appears to be largely based on "original research" which doesn't belong here. AstroLynx (talk) 10:50, 14 May 2015 (UTC) (ec)My mistake. I see the objection is not to this bit, it's to the bit above. Nobody claimed it was badly written when it was part of a stable version five years ago. 156.61.250.250 (talk) 10:54, 14 May 2015 (UTC) You said it was badly written. Now you claim it's original research. You seem to be making this up as you go along. The fact is that the change in delta t and the secular acceleration of the moon has been known for years. 156.61.250.250 (talk) 10:58, 14 May 2015 (UTC) Actually it is both (original research as there is no reference and it is badly written - the cited numbers 84 and 19 come from nowhere). The fact that it was there five years ago is not relevant - it was evidently removed for the reasons which I mentioned just now. Changes in Delta T and the secular acceleration of the moon are indeed well known but you do not provide references for your claim. AstroLynx (talk) 11:03, 14 May 2015 (UTC) It was removed as part of a batch by an editor claiming the article had been edited by a sockpuppet. The content was never questioned. 156.61.250.250 (talk) 11:45, 14 May 2015 (UTC) Then why is it unsourced and badly written (see my earlier comments). Such content does not belong in WP. AstroLynx (talk) 11:54, 14 May 2015 (UTC) I don't see it's badly written. Lichtenberg theorised a mixture of 200 and 300 - year correction steps. The actual error to be compensated is one day in about 210 years, so there will be many more 200 than 300 - year steps. The actual ratio turns out to be 84 to 19, but that's a side issue that doesn't affect the structure of his scheme. 156.61.250.250 (talk) 12:09, 14 May 2015 (UTC) If the section which I deleted comes from Lichtenberg's paper this should be indicated more clearly. Still I do not feel that this level of detail belongs here, perhaps it should be moved to Reform of the date of Easter. AstroLynx (talk) 12:26, 14 May 2015 (UTC) The consensus is that this level of detail does belong here. 156.61.250.250 (talk) 13:45, 14 May 2015 (UTC) Kindly provide some proof of your claim. AstroLynx (talk) 13:58, 14 May 2015 (UTC) It was a stable version five years ago. 156.61.250.250 (talk) 15:21, 14 May 2015 (UTC) That is a very long time ago. So apparently nobody objected to its deletion five years ago? You still have not given any evidence that the deleted section is from Lichtenberg's paper. AstroLynx (talk) 15:42, 14 May 2015 (UTC) Obviously it's not word - for - word because that would be plagiarism. As for your other point, doubtless many editors objected to the loss of their work when Jc3s5h arbitrarily turned the clock back. 156.61.250.250 (talk) 15:55, 14 May 2015 (UTC) Lichtenberg describes the replacement of solar equations (common centennial years) and lunar equations (drift of one tithi in 312 1/2 years) with a unified correction cycle which provides the same number of epact corrections over the cycle. — Preceding unsigned comment added by 156.61.250.250 (talk) 16:20, 22 May 2015 (UTC) You must be referring to another paper by Lichtenberg or someone else. I have read the Lichtenberg (2003) paper twice and I don't see anything which matches your claim. AstroLynx (talk) 10:44, 23 May 2015 (UTC) He most certainly does use unified corrections (200 and 300 year steps). How do you claim he makes the adjustments? 156.61.250.250 (talk) 12:49, 23 May 2015 (UTC) Lichtenberg's (2003) paper indeed discusses the lunar and solar corrections which are necessary to compute the correct lunar age but the section which I blanked is not a part of his paper as you claim. If you think that the blanked section (which I repeat here) Using a more accurate leap year rule (218 leap years in 900 years with AD 2500 a leap year) the present system has a "lunar jitter" of 2.60 days. The unified correction cycle repeats every 22500 years starting in 1 BC. In this period there are 175 Gregorian solar corrections and 72 lunar ones for a net correction of 103 days. There are nineteen 300 - year correction periods interspersed among eighty - four 200 - year ones. These numbers are unforgettable - 84 is the number of years in the British epact cycle before the Synod of Whitby and 19 is the number afterwards. The 300 - year periods end in 1100, 2400, 3500, 4800, 5900, 7000, 8300, 9400, 10700, 11800, 13100, 14200, 15500, 16600, 17700, 19000, 20100, 21400 and 22500. In the first three millennia of the Christian era the lunar jitter is 3.16 days, which cannot be reduced by moving corrections which would otherwise occur in leap years. The cycle is furthest behind the moon in the 11th century and furthest ahead in the 22nd century. is a part of his paper, please indicate where. AstroLynx (talk) 13:57, 23 May 2015 (UTC) That's not what I asked you. My question was, does he or does he not make use of unified corrections in spaced out 200 - and 300 - year intervals to replicate the 43 epact corrections in 10 000 years? 156.61.250.250 (talk) 14:16, 23 May 2015 (UTC) You're sidestepping the issue. The issue is the section which I blanked because it is unsourced and you keep on trying to put back. Up to now you have not be able to provide a verifiable source. AstroLynx (talk) 14:26, 23 May 2015 (UTC) It's you who is "sidestepping the issue". I happen to know that's exactly how he did it. 156.61.250.250 (talk) 14:43, 23 May 2015 (UTC) Provide a verifiable source then. AstroLynx (talk) 14:58, 23 May 2015 (UTC) The verifiable source is obviously the paper itself. 156.61.250.250 (talk) 15:03, 23 May 2015 (UTC) Sorry to puncture your balloon, but as I already indicated above the blanked section is nowhere to be found in Lichtenberg (2003). How long do you want to keep on this farce? I can keep up just as long as you can. AstroLynx (talk) 15:08, 23 May 2015 (UTC) As your parachute deflates, you can ponder that there is no requirement that ideas should be reported in the precise words of the person who originates them.156.61.250.250 (talk) 15:20, 23 May 2015 (UTC) The problem is that most of the numbers and years listed in the blanked section are nowhere mentioned in Lichtenberg's (2003) paper. Nor is the Synod of Whitby anywhere referred to in the same paper. How can you claim that your text is a selective rephrasing of Lichtenberg's paper? I am seriously beginning to doubt whether you have ever read the Lichtenberg paper you are claiming to cite. AstroLynx (talk) 15:38, 23 May 2015 (UTC) As I say, it doesn't have to be exact. To say that "most" of the years are different is not good enough. Please list specifically the years which you find to be different. 156.61.250.250 (talk) 15:44, 23 May 2015 (UTC) OK, which table or page lists the years 11800 and higher? Where is the Synod of Whitby mentioned? Where are the values for lunar jitter mentioned? Unless you can provide specific page numbers from Lichtenberg's (2003) paper mentioning these numbers, I can only conclude that it is unsourced. AstroLynx (talk) 16:02, 23 May 2015 (UTC) As I pointed out, Lichtenberg does the calculation over 10,000 years so you wouldn't expect to see years 11,800+ appearing in his data. You can still provide the data for earlier years. 156.61.250.250 (talk) 12:09, 24 May 2015 (UTC) So you finally admit that most of the numbers and years listed in the blanked section are not found in the Lichtenberg (2003) paper but are based on original research (probably yours?). I still seriously doubt whether you have actually read Lichtenberg's paper. As I became interested in the reason why you persist in having this section restored I had a closer look at the original edit on 10 June 2010 by IP 94.194.22.179, one of the known London-based sockpuppets of Vote (X) for Change. Comparing the latter's editing behavior (and that of his numerous sockpuppets) with yours has been very insightful and revealing - it explains so much. AstroLynx (talk) 12:57, 24 May 2015 (UTC) What a load of rubbish! I drew attention to the "sockpuppet" issue earlier in this thread. The section was declared kosher five years ago so you have a high bar to overcome to remove it. You're creating a diversion by throwing mud around in the hope that some will stick. If you're not prepared to justify your position by detailing the "discrepancies" you allege you can be dismissed as just a troll. I object to people removing good content for spurious reasons. This subject was extensively discussed in the archives - I suppose Karl Palmen, Tom Peters and the rest are all sockpuppets as well. 156.61.250.250 (talk) 13:17, 24 May 2015 (UTC) Despite your whining you still have not provided a verifiable source for the blanked section - original research doesn't belong in WP. The blanked section never was 'declared kosher' five years ago as you claim - it was repeatedly removed after your sockpuppets tried to put it up again and again. If I were you I would also start worrying about your recent additions to Iranian calendars. I have noticed that you have added quite a lot of unsourced text in recent days. If you do not start adding verifiable sources soon I will remove most of it - including the sections which appear to be original research. AstroLynx (talk) 15:24, 24 May 2015 (UTC) Nah, it was added once and there it stayed. I think we can assume from your reticence that the dates in the first ten thousand years are in agreement with those in the paper. 156.61.250.250 (talk) 15:36, 24 May 2015 (UTC) Why don't you check yourself - you claim to have read the Lichtenberg paper. AstroLynx (talk) 15:43, 24 May 2015 (UTC) Information like that is not something you would commit to memory. 156.61.250.250 (talk) 09:00, 27 May 2015 (UTC) You should have kept notes. If you had access to the Lichtenberg paper five years ago, you should be able access it again now. AstroLynx (talk) 09:49, 27 May 2015 (UTC) This is typical of your attitude. Looking at your editing history I see you've tried this trick before. When someone wants to do an end run around Wikipedia policy it's they who have to do the legwork. We have a verified stable version which you want to change. In the previous incident you were trying to skate round WP:V. Editors pointed to sources which they wanted to include in an article and you pointed to a book which you claimed supported your viewpoint. Asked to support this by quoting the relevant passage you said you didn't have a copy and would order it through the library but You will have to ask this nicely and include the magic word. Later, when an editor referred to the book you quoted from it instantly, thus proving that you had had a copy of it all the time. You exhorted the editor to get a copy of the book: Why don't you prove me [Vgent] wrong by looking it up for yourself? That's not what good faith, collegial editing is all about. The incident related to an attempt by you to exclude the other editors' sources from a description of a picture of Muhammad. You have this picture on your web profile. You are arguably obsessed with it. 156.61.250.250 (talk) 10:55, 27 May 2015 (UTC) You are the person who wants to put his original research up, so you must provide the correct references. You cannot expect that other editors will do this for you. That fact that you seem to be unable to do this clearly proves that you actually never saw the Lichtenberg paper which you claim is your source. Your editing behaviour during the past few days on this page has thus clearly shown that you are a liar and a fraud. It is interesting that you refer to the discussion on the Islamic calendar page with IP 87.81.147.76. For any editor it should be clear that this IP's editing behaviour is exactly the same as yours, which, for me at least, makes it abundantly clear that you the same person. Yet another London-based sockpuppet of Vote (X) for Change. AstroLynx (talk) 11:21, 27 May 2015 (UTC) Wow. Every editor in a university city of ten million with an interest in calendars is a sockpuppet. You say a stable version is original research. Proof? I see that 87.81.147.76 was supported by other editors, so I suppose that makes them liar(s) and (a) fraud(s) too. An editor (not talking of me) uses the word "disingenuous": The RFC closing statement didn't deal with the NPOV concerns, hence shouldn't be relevant to this discussion. Also, Hillenbrand's "sectarian" conclusion is notable, and usually the sole reason why reliable sources refer to his paper and this image set. It is disingenuous to ignore his conclusion and pass this image/MS. as neutral. Speaking of you he says: Your assessment is not entirely accurate. Hillenbrand didn't see a need to examine the other two images (note the word "already" in his conclusion). Also, the third image that he used to prove the "strong sectarian feeling" (The Envoy of Musailama) has nothing to do with the investiture of Ali. Incidentally, his arguments concerning that image also applies to this image (the prominent placement of ahl al-Bayt; al-Hussien is favored over al-Hassan by being placed closest to the prophet; etc). I didn't get your last point though, since the image is still relevant in the book's own page or where an example of sectarian or polemical art is needed. And again: Well, it was clear enough that you misrepresented Hillenbrand. He actually noticed a "strong sectarian feeling" in an image that was not about the investiture of Ali, contrary to what you wrote above. Then based on how you misrepresented the source you assumed that the RFC image has no sectarian purposes, which is original research (and can be disputed by pointing at Hillenbrand's arguments about the Envoy to Musailama). In any case, I don't see a reason why I should change my !vote. Adding pages/images to a general article from a source that has been described as sectarian and agenda driven is not inline with npov. And again (of one of your supporters): You actually missed an important argument. The image is found in a book that was illustrated for sectarian and polemical purposes. I would expect the closing party to justify why polemical/sectarian imagery/works should be given space in this article. And again (of another of your supporters): Actually, the image is being used here in the same context that reliable sources have described as sectarian (i.e., illustrating a neutral text about calendars). So your claim that it's "being used in non-sectarian/non-polemical ways" is nonsensical. Your 2nd point shows that you have very little experience in content editing. We are not supposed to give preference for one source and ignore others. In this case, reliable sources differ on caption and pertinence. This article must reflect these differences to meet WP:NPOV. As the discussion unfolded it emerged that none of your supporters had read any of the books which their arguments relied on but you did not call them "liars and frauds". 156.61.250.250 (talk) 13:42, 27 May 2015 (UTC) I'm stepping in to this argument because it's getting really stupid. First of all, as per WP:BURDEN: "The burden to demonstrate verifiability lies with the editor who adds or restores material, and is satisfied by providing a citation to a reliable source that directly supports the contribution... The citation must clearly support the material as presented in the article." Since 156.61.250.250 is the one restoring the content they must prove that the citation supports the material, and based on what I have read above they have failed to do so. Secondly, past arguments shouldn't be intruding on this page. At any rate, this discussion isn't moving anywhere. If 156.61.250.250 cannot provide a quote from Lichtenberg to support their case then as far as I'm concerned the material is unsourced. Arcorann (talk) 02:25, 28 May 2015 (UTC) What happened back in 2010 is that the material was added and found to be policy - compliant. That's why it became a stable version. Then in the back - and - forth of editing it got removed and came back. Obviously this does not mean that the person who happened to restore the material at any point in time is lumbered with going through the whole verification process again. 156.61.250.250 (talk) 13:50, 28 May 2015 (UTC) I will also step in to say that what happened 5 years ago is procedurally irrelevant. If the desired material was supportable then, then it is still supportable, excepting only additional work that overturned it. Whether or not it was backed up by citation then, it needs to be backed up by citation now. If numbers and calculation is required, the source must provide it. It comes down to put up or shut up, because editorial opinion is insufficient, sockpuppet or not. Evensteven (talk) 20:12, 28 May 2015 (UTC) Just because the material was in a stable version does not imply that it is correct or policy-compliant - I know that factually incorrect material can persist in a supposedly stable version for a long time, having corrected a few such errors myself. As per the section I quoted of WP:BURDEN, if you're restoring material and it's challenged you must be able to go through the verification process and show that a source exists, regardless of whether it has appeared in the article before. As said by Evensteven, if it's supportable then it's supportable now, and your failure to support it now suggests that it wasn't supportable then either, and that its removal was a correct decision. Arcorann (talk) 00:51, 29 May 2015 (UTC)

More or less as an aside, when I was learning computer programming

(Specifically COBOL -- this was in the antediluvian days when the IBM 370 was popular), I had to write a program to determine which day of the week a given date was. The way I did it was first to work out by hand that January 1st of the year 1 was a Saturday, count the number of days since then (and I dropped the 11 days in 1752 when Britain switched from the Julian calendar to the Gregorian calendar), do modulo 7 on the number, and there we were. My instructor thought it was an ingenious way of doing it. JHobson3 (talk) 19:25, 18 January 2016 (UTC)

Do we need an algorithm for a revised Easter Day computation?

In the past weeks two editors have been adding material criticizing existing Easter Day computations and promoting a revised Easter Day algorithm recently published by one of the editors in a rather dodgy journal. I do not believe that such material belongs here but before I start deleting all this material I would like to hear the opinions of other editors. AstroLynx (talk) 13:25, 10 February 2016 (UTC)

Wikipedia cautions strongly against primary sources. Unless these methods have been peer-reviewed in reputable sources, they may be mentioned and linked to, but should not receive the extensive coverage they occupy now. -- Michael Bednarek (talk) 18:13, 10 February 2016 (UTC)

My understanding from reading the material is that the author believes that their algorithm produces "better" Easter dates than the Gregorian algorithm. If so, then not only are their supposed criticisms invalid (the algorithms given calculate Gregorian Easter, which is correct - see also Stockton who has tested many algorithms, including ones based on the original source), but also the content should fall under WP:FRINGE and therefore be eliminated. Arcorann (talk) 11:43, 16 February 2016 (UTC)

Or more likely WP:UNDUE. At any rate, I've removed the content. The person is free to make their case here if they disagree. Arcorann (talk) 12:33, 16 February 2016 (UTC)

No Full Moon

I notice that over and over again editors pervert the Easter rule by introducing an (ecclesiastic) Full Moon. This is misinformation. Surely popular and astronomical secondary sources mention a Full Moon, but canonical literature from Dionysius to Clavius has always only been based on the 14th day of the lunar month, following from the definition of Jewish Passover. That this happens to be close to the day of Full Moon for a properly aligned lunar calendar (which the ecclestiastic reckoning is not), is circumstantial. Referring to the "Full Moon" has led only to misguided attempts to "improve" the computation of Easter.

I noticed only now that my latest attempt (7 Jan. 2015) to clarify things was quickly (26 Jan.) destroyed by an anonymous editor without further comment. I may try again in the near future to repair this when I have time, but can all those editors who feel the urge to "improve" this article please first read up on the relevant literature and not put in misguided misinformation?

Tom Peters (talk) 12:41, 22 February 2016 (UTC)

The downside of an encyclopedia that everyone can edit is sometimes that everyone can edit it. That IP editor, 156.61.250.250, has been blocked soon after their edits here. If you think the current wording is wrong, the obvious recourse is to correct it – preferably with citation of reputable sources. -- Michael Bednarek (talk) 02:33, 23 February 2016 (UTC)

Excel formulas

The Excel formulas under the Software heading deliver different results. It should be stated that they have different scopes. The formulas

=ROUND(DATE(A1,4,1)/7+MOD(19*MOD(A1,19)-7,30)*14%,0)*7-6

and

=FLOOR((4&-A1)-DAY(5)+97%*MOD(18.998*MOD(A1+8/9,19)+INT(68%*INT(A1%)-INT(A1%/4)-5/9),30),7)+DAY(1)

differ in 5802 of the 8100 calculations for the years 1900-9999. The latter formula is the correct for those years while the former is probably only intended for the years 1900-2199 for which it is also correct. The difference is always a (positive or negative) multiple of 7 days, i.e. they both get the day of week right but not the week itself. Presumably it omits correcting for the period of the orbit of the moon. The first error occurs in the year 2204 which is why it might go unnoticed for a while. Other well-known formulas that contain errors include the formula

=FLOOR(A1&"-05-"&DAY(MINUTE(A303/38)/2+56);7)-34

from "Excel 2010 Tips & Tricks" by John Walkenbach and other sources which makes 5790 errors in the year range 1900-9999, the first one occurring already in the year 2079. Thus, it is not even intended for the period 1900-2199.

A final comment about the 9999 year formula is that it is not compatible with international date standards - FLOOR((4&-A1) must be replaced by FLOOR((A1&-4) for non-US date formats. — Preceding unsigned comment added by 31.15.60.198 (talk) 17:08, 22 March 2016 (UTC)

The scope of the longer formula is not only the full range of years, it also works in Excel files with both file formats - the 1900 (Standard) and the 1904 file format.

In 1998/99 there was a contest in Germany, to get the shortest Excel formula for 1900-2078 in the 1900 file format. Most formulas you can find in the www, are from this and do not care about 2079-9999 or the 1904 file format.

13:55, 27 April 2016 (UTC) — Preceding unsigned comment added by 85.199.76.137 (talk)

Software - old school solutions and methods are dominating

Most of software solutions are based on the equation sets of Gauss and his epigones.
These sets were made for mental arithmetic.
Modern software products are able to calculate the Easter Sunday date from the year in one step, short, and efficient.

The "mental arithmetic" algorithms will long outlive what follows

Yes, but the "mental arithmetic" will be of use indefinitely, long after the ephemeral modern languages and applications that follow come to dwell amongst the doornails; then, the "mental arithmetic" algorithms will be needed to create programs that execute in the future. Vincent J. Lipsio (talk) 01:19, 20 July 2016 (UTC)

Open Office - Calc (Gregorian, 1583-9957)

=EASTERSUNDAY(A2)

EASTERSUNDAY(year) works in LibreOffice as well as OpenOffice. Roches (talk) 14:55, 10 July 2016 (UTC)

Visual Basic and VBA(Gregorian)

Public Function EASTERSUNDAY(y As Integer) As Long ' for 1900-9999 as serial number
   EASTERSUNDAY=7*((CDate(y &-5)+.967*(18.99*(y Mod 19+732)+(y\100)/1.472\1-y\400)Mod 29)\7)-34
End Function

Public Function EASTERSUNDAY(y As Integer) As String ' for 1500-9999 as string
   EASTERSUNDAY=CDate(7*((CDate(y &-5)+6*(y<1900)+.967*(18.99*(y Mod 19+732)+(y\100)/1.472\1-y\400)Mod 29)\7)-34)
End Function

MS Access (Gregorian)
a) for 1900-9999 as serial number (date)
=7*((CDate([year]&-5)+,967*(18,99*([year]Mod 19+732)+([year]\100)/1,4718\1-[year]\400)Mod 29)\7)-34)
b) for 1500-9999 as string
=CDate(7*((CDate([year]&-5)+6*([year]<1900)+,967*(18,99*([year]Mod 19+732)+([year]\100)/1,4718\1-[year]\400)Mod 29)\7)-34)

MS Excel (Gregorian)
a) for standard 1900 file format (1900-9999)
=FLOOR((A2&-8)-MOD(30*INT(11*MOD(A2,19)-68%*INT(A2%)+INT(A2%/4)+44.55),29.032),7)-97

b) for 1900 and 1904 file formats (1904-9999)
=FLOOR((A2&-5)-MOD(30*INT(11*MOD(A2,19)-68%*INT(A2%)+INT(A2%/4)+44.55),29.032)-DAY(6),7)+DAY(1)

15.211.201.89 (talk) 21:46, 19 July 2016 (UTC)