Talk:Zeller's congruence

message: Heading added for structural reasons. 82.163.24.100 (talk) 23:31, 19 January 2009 (UTC)
thread_title:  An old comment, which should go 

message: In the simplified version it mentions to adjust year by 1 and month by 3 for January and February. However, implementing this gives incorrect results. I think it should be year -1 and month + 12 (to get months 13 and 14) same as with the normal algorithm.  — Preceding unsigned comment added by 2601:2C1:280:2E5A:1552:40CA:BAE0:F65B (talk) 14:16, 25 March 2022 (UTC)
replies: text: You are correct, and it looks like somebody fixed that. MiguelMunoz (talk) 22:39, 18 September 2023 (UTC)
thread_title:  Simplifications Error? 

message: The article makes this ambiguous claim:
Both of these differences can be accounted for by replacing the term \left\lfloor\frac{J}{4}\right\rfloor - 2J with the term 5 - J, or 5 + 6J to avoid negative numbers. 
Huh? I'm not sure when I'm supposed to replace what, and neither of these looks right. To avoid negative numbers, the -J may be replaced with +6J and the -2J may be replaced with +5J. The J/4 term doesn't need to be touched. Also, this point doesn't belong in an explanation of the difference between the two formulas. I also don't know what is meant by "both these differences..." --MiguelMunoz (talk) 06:23, 19 February 2008 (UTC)
thread_title:  Avoiding negative numbers 

message: Some of the old comment in this page is no longer needed.  Perhaps the "Chief Maintainer" could remove that which is not worth keeping? 82.163.24.100 (talk) 10:26, 23 June 2008 (UTC)
thread_title:  Old Discussion 

message: Joe Kress: Why did you remove the examples? The transition from February to March is a major point of confusion, and I put in two good examples to clarify the point. If you have a problem with them, let's discuss it here. --MiguelMunoz (talk) 17:19, 20 February 2008 (UTC)
replies: text: I have no idea what happened, but I had no intention of removing the examples. I am readding them with some wikification. — Joe Kress (talk) 23:27, 20 February 2008 (UTC)
replies: text: Okay. That's cool. Thanks for putting them back. --75.5.4.210 (talk) 07:42, 21 February 2008 (UTC)
thread_title:  Examples 

message: Someone has edited the references section.  The addition of the "doi" link for the 1886 paper looks confusing to me.  I suggest that it be given a "blob line" of its own, independent of any merlyn reference.  The note at the beginning of the section will then be restored to the accuracy that it originally had. 82.163.24.100 (talk) 22:20, 11 September 2009 (UTC)
thread_title:  References 

message: Is there a variant of Zeller's congruence available for the Revised Julian calendar, and if so how can we source it for putting it in? It would be straightforward to work it out, but that would be original research and banned - even though the actual result would be no different from one found elsewhere. PMLawrence (talk) 12:56, 14 January 2010 (UTC)
replies: text: Zeller did not and could not have developed such an algorithm because he developed his algorithms before the Revised Julian calendar was invented, so it cannot be a Zeller's congruence. If one was later developed, it would have to include Zeller in its name to be included here. — Joe Kress (talk) 20:50, 14 January 2010 (UTC)
replies: text: On the first point, that's why I used the expression "variant of Zeller's congruence". On the second, there is no need for it to be called that, so long as the connection and relevance were pointed out. But none of this addresses where and how we could get it without tripping over the formal original research barrier. PMLawrence (talk) 02:40, 15 January 2010 (UTC)
thread_title:  Revised Julian calendar 

message: Hello fellow Wikipedians,
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thread_title:  External links modified 

message: A beautiful formula devised by a Filipino Mathematician (Dave Ryan Cariño) is an algorithm using direct substitution without any condition that is applicable from year 1582 onwards.
Let: 
     M as Month of the year (1 = January, 2 = February, ………, 12 = December)
     D as day of the month (1 to 31)
     Y as year (1582....∞)
     D.D as day of the date (0 to 6, 0=Saturday, 6=Friday)
     J = (12Y+M-3)/1200
 D.D = { 3M + 4 + D - ⌊3M/7⌋ - 2⌊(M+7)/10⌋ + ⌊(50Y+M-3)/40⌋ - ⌊J⌋ + ⌊J/4⌋ } mod 7
 Example 1: October 15, 1582, first day of Gregorian calendar.
 M = 10, D = 15, Y = 1582 
 J = [(12(1582)+10-3)]/1200
   =  18991/1200
   = 15.825833
 D.D = { 3(10) + 4 + 15 - ⌊3(10)/7⌋ - 2⌊(10+7)/10⌋ + ⌊[50(1582)+10-3]/40⌋ - ⌊15.825833⌋ + ⌊15.825833/4⌋ } mod 7  
   = { 30 + 4 + 15 - ⌊4.2857⌋ - 2⌊1.7⌋ + ⌊1977.675⌋ - ⌊15.825833⌋ + ⌊3.956⌋ } mod 7  
   = { 30 + 4 + 15 - 4 - 2 + 1977 - 15 + 3 } mod 7  
   = { 2008 } mod 7  
   = 6 ;Friday
 So, October 15, 1582 is Friday
For Julian Calendar: 
                                             
D.D = { 3M + 2 + D - ⌊3M/7⌋ - 2⌊(M+7)/10⌋ + ⌊(50Y+M-3)/40⌋ } mod 7  — Preceding unsigned comment added by Vincent22914 (talk • contribs) 11:51, 17 January 2018 (UTC)
thread_title:  '''Cariño's Algorithm''' 

message: The "Other Variations" section give four alternatives, but two of them seem to be missing something. The source for the variation by Michal Keith involves changes to the day, and doesn't always work in my tests. The same goes for the JR Stockton variation. When I compare each of these with the standard (13m+1)/5, I get these values for each month: (I adjusted Stockton and Tøndering for "Sunday is Zero.) For Michael Keith, a difference of 1 corresponds to a value of 2 for Sunday. Only Claus Tøndering's variation works. It looks there are missing details on the other two variations. (I also added some text to clarify that Tøndering's variation also used 0 for Sunday.)
Michael Keith:
month 3: delta = 1
month 4: delta = 1
month 5: delta = 1
month 6: delta = 1
month 7: delta = 1
month 8: delta = 1
month 9: delta = 1
month 10: delta = 1
month 11: delta = 1
month 12: delta = 1
month 13: delta = 1
month 14: delta = 0
JR Stockton:
month 3: delta = 2
month 4: delta = 2
month 5: delta = 2
month 6: delta = 2
month 7: delta = 3
month 8: delta = 2
month 9: delta = 2
month 10: delta = 2
month 11: delta = 2
month 12: delta = 3
month 13: delta = 2
month 14: delta = 2
Claus Tøndering:
month 3: delta = 0
month 4: delta = 0
month 5: delta = 0
month 6: delta = 0
month 7: delta = 0
month 8: delta = 0
month 9: delta = 0
month 10: delta = 0
month 11: delta = 0
month 12: delta = 0
month 13: delta = 0
month 14: delta = 0
 MiguelMunoz (talk) 22:53, 18 September 2023 (UTC)
thread_title:  Problems in "Other Variations"