Talk:Perpetual calendar

message: Old Redirection: Talk:International_Fixed_Calendar
I have removed the redirection from this talk page because I believe it to only be tangentially and not directly related to this topic. --Stux 21:50, 22 October 2005 (UTC)
thread_title:  Removed Redirection 

message: I think this entry should have an example of the gregorian calendar or even formulas themselves.  At the very least links to online perpetual calendars would be useful.  I found one here by searching Google but I don't know if its a good example to link.  If it had days of the week explictly listed, it would be more useful. --Stux 21:50, 22 October 2005 (UTC)
thread_title:  Example Perpetual Calendar 

message: I added an example of a formula that can be used to create a perpetual calendar. I added some links to my web site and then discovered that I did not use the formula in the javascript. I then removed the links. Denmarks 21:21, 12 February 2006 (UTC)
thread_title:  Perpetual Calendar Formula 

message: I'd like to see some information on how mechanical watches implement perpetual calendars. 218.215.32.173 16:27, 6 January 2007 (UTC)
thread_title:  Perpetual calendar in watches? 

message: …translate the content from :ru:Вечный календарь? — 87.236.197.182 08:23, 22 February 2007 (UTC)
thread_title:  Could anyone… 

message: It is very easy to combine things like those. See for instance a program simply called "Calendar" written in 1993 that does those things and more. It will give the correct day of the week since the start of the Gregorian Calendar (October 15, 1582) until the year 9999. That year was not chosen as the year the algorithm would break by the author, but only to put some arbitrary limit of 4 digits for a year. The program does other calendar-related calculations as well:  97.103.81.29 (talk) 00:27, 28 October 2008 (UTC)
thread_title:  Perpetual calendar and Easter (and Friday the 13th) 

message: After literally years of frustration trying to do date math in spreadsheets, I'm collecting all the date calculations I can find/create into one spreadsheet and publishing it. I came here in search of a single fundamental algorithm. This may be it but, after reading it several times. it's still not clear how this works.
Thank you for writing this article. It really sounds like whoever contributed knew what they were talking about. I want to rewrite it so the average person could understand it. How can we make it so it's less dense. It's written by someone who understands the subject matter for others who understand the subject matter. It needs to be stepped down to a level below that of a professional so students can get it too. 
--PB--
Netscr1be (talk) 15:08, 3 January 2011 (UTC)
thread_title:  Required math skills & Reading Level too High 

message: Dear Mr.Netscr1be, my english is not good, sorry. Please see by http://commons.wikimedia.org/wiki/Category:Perpetual_calendars the file "Permanent_Calendar" and http://commons.wikimedia.org/wiki/Wikitable_calendar. Here is a simple solution. The result is very easy to control. The algorithm is: The days of the week for January and February are the first line in the second from February through December. I wish you much fun. greetings from saxony Karl Nimtsch --LenderCarl (talk) 13:22, 7 February 2011 (UTC)
thread_title:  Algorithm for a Perpetual calendar 

message: I’ve added the section “Mental calculation” to show the practical method useful to exploit the preceding sections while performing mental calculation. The method, being optimized exactly for this aim, coincides with the preceding sections only at the level of formulas, not at the operative level: therefore it’s needed to explain its operative details also with some examples (the preceding sections can be considered exploitable at the best by computer implementations, surely not by human calculation). 
The location of the section appears correct since it simply clarifies how to use the preceding formulas with no available calculator (and perhaps spending less time than using a calculator). The page “Determination of the day of the week” is not suitable for locating the method explanation since it describes a wide variety of formulas and methods without concerning mental calculation, while this page “Perpetual calendar” introduces the same tables used by the method (though not optimized for human calculation).
Moreover, the section shows the method for both ways a person can “imagine” a week, that is starting with Sunday (like in USA and other nations) or with Monday (about twice the nations with respect to Sunday); the apparent duplication of some parts is due to show the method without elements which can interfere with memorization of the method itself.
But after some weeks I found the whole section deleted by (anonymous) 92.233.138.249 with the following explanation:
"This is essentially a repetition of the "Perpetual Julian and Gregorian calendar table. Using essentially the same system but starting the week on Monday creates confusion" .
These words indicate that he/she was completely missing the aim of the introduced section, not focusing on its optimization for mental use neither considering that many people use Monday as first day of the week.
For these reasons, I reintroduced the deleted section in the same position.
Antonio Musarra (talk) 23:38, 25 October 2018 (UTC)
replies: text: , you might like to read about citing a reliable source. Justlettersandnumbers (talk) 09:46, 26 October 2018 (UTC)
thread_title:  "Mental calculation" section 

message: This has been changed twice by an anon, and reverted twice by me. I'm explaining  here in case that anon might be checking the talk page. I'll create a talk page for him and ask him to look at this in case he checks there.
The two changes made so far by the anon can be seen at  and . He contends that Wednesday is correct, though the article says it would be Tuesday. I have reverted these two edits. He cites sources, but those sources are for a Gregorian calendar (see , which is the relavent page for a later edition of one specific source he cites). The example he is changing is, as I read the article,for a Revised Julian calendar. I've edited the article a bit to try to make this clearer. Wtmitchell  (talk) (earlier Boracay Bill) 22:45, 10 November 2018 (UTC)
replies: text: Yes, I wonder if the Revised Julian calendar details are all that important in this context. Perhaps this stuff should be shunted off into Revised Julian calendar. Thincat (talk) 23:18, 10 November 2018 (UTC)
thread_title:  Day of the week example for 27 January 8315 

message: I'm a historian, and I just needed to note in 92.234.23.201's reference to October 1582, it's not a factual absolute that October 1582 only had 21 days. That idea is an anachronism, the irony of which, in a discussion about days and time, boggles my mind.
ONLY if you were a European Roman Catholic did October 1582 have 21 days. If you were French, a European Protestant, or a non-European, October 1582 had 31 days.
This was not a universal change in its time. Therefore, referring to it as a universal change when discussing the calendar is an anachronism.
92.234.23.201, you noted the change in the name of the calendar from Julian to Gregorian without noting the why of the name change, or from where that name comes, and this is important for accuracy. Julian comes from Julius Caesar, of course, but Gregorian comes from POPE GREGORY XIII, at whose direction the new calendar was developed, after centuries of debate and whining within the Church over the matter of miscalculations caused by the Julian calendar, to finally make Easter 1582 retroactively fall on the date prescribed by the 4th century Council of Nicaea. Easter was being celebrated on the wrong day for centuries, but the Church was reticent to do anything about it. The 1562-3 Council of Trent gave the Church the authority to stop the hand-wringing and do something about it. It took a couple more decades, but finally, Pope Gregory XIII, working with Italian scientist Luigi Lilio and Jesuit mathematician/astronomer Christopher Clavius, fixed the calendar problem or problem calendar. The reason they chose October? Any Catholic can tell you, there are no major Holy Days in late October.
However, this was at a time of great unrest in the Christian world. Luther had just posted his 95 Theses in 1517 (ironically, in October); only 2 years after that, you have the rise of Calvinism, then the teachings of Zwingli that lead to Presbyterianism; by 1525, you have the beginnings of the Anabaptists, the Mennonites, etc., etc. Do you think for a moment that they are going to change their calendars just because the POPE says so? Even within the Roman Catholic world, a change that huge wasn't implemented at the same time that the papal bull recommended; France, for instance, waited until the end of the year to make the change.
That's why I'm saying, glossing over the calendar's name change leads to this inaccurate assertion that WORLDWIDE, October 1582 had 21 days. THAT IS JUST NOT ACCURATE.
The changes to the calendar were adopted at different times in different places. This means you CAN'T make blanket statements about days and dates for the past unless you know the geolocation of the matter on which you are speaking. From October 1582 until 1752, you can't generalize about days and dates; 1752 is the latest date I know of that the Gregorian calendar was adopted on the globe, which was by the British Empire.
If you all want to continue to argue about what date June 6, 6666, will be, have at it. That date will mark 4700 years since my Uncle Ronnie's death, by the way, so please remember him on that day, whatever day it is. 
But when you speak of the past, between October 1582 and 1752, you are treading on quicksand if you make generalizations. Just look within Wikipedia itself - many famous figures in European history have 2 birthdates in that time period: their Julian birthdate (often called "old style"), and their Gregorian birthdate. Whichever calendar was in use in their geolocation at the time of their birth, that's what day they considered to be their birthdate. It's anachronistic to consider anything else.Kelelain (talk) 14:13, 29 September 2023 (UTC)
thread_title:  Reference to October 1582 - just a note from a historian about anachronisms & calendar absolutes between 1582 & 1752