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Talk:Holidays related to Easter: Difference between revisions

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Talk:Holidays related to Easter (view source)

Revision as of 04:22, 4 June 2011

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Whose Easter are we calculating here? Or, more specifically, which calendars are we using? (And, when do we switch from Gregorian to Julian?) According to Wikipedia, depending on the answers to these questions we can have easter in March, April or May. The sample output from the Algol 68 program makes me think that we are supposed to calculate what wikipedia calls the "Western Christianity"'s Easter, but that was just one of the issues which cause different people to assign different dates to easter in the same year. I think a full specification would be appropriate here. (Easter is apparently the first sunday after the 14th of the month where it occurs, but I am confused about how you unambiguously determine which month it occurs in. But I am also having problems reconciling this "first sunday after the 14th of the month" rule with easters which occur in the first week of April.) --[[User:Rdm|Rdm]] 14:40, 29 June 2010 (UTC)
 
: It's the first Sunday after the 14th day of the ''lunar'' month. That is, the first Sunday after the full moon, specifically, the full moon after March 21st. --[[User:Markjreed|Markjreed]] 04:22, 4 June 2011 (UTC)
 
: It's horribly complicated as it's ''usually'' the Sunday of the weekend after Passover, but is calculated using different rules to those specified in the Torah. And it's been the subject of a number of major fights in the Christian church (e.g., the Council of Nicaea). So I searched around and ended up using the code at the end of http://www.assa.org.au/edm.html (which I ''think'' is based on doing the switch to Gregorian rules using the British date; you should be able to confirm from the tables higher up that page) as that at least gives the same days/months as that deeply impenetrable ALGOL code for the dates in the exact challenge. –[[User:Dkf|Donal Fellows]] 10:34, 30 June 2010 (UTC)
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:: Not only is it horribly complicated (or rather not clear), arguments over how to do it split the church (the excommunication of the Quartodecimans which sounds like something out of Ghostbusters) and almost started conflicts. See [http://mangsbatpage.433rd.com/2008/03/calculating-easter.html] --[[User:Dgamey|Dgamey]] 22:27, 8 July 2010 (UTC)
<br>I was thinking of adding a Python calculator for future easters that relied on the random module :-)<br>--[[User:Paddy3118|Paddy3118]] 13:07, 5 July 2010 (UTC)
 
::: To be fair, Easter calculation is a bit complex, but not "horribly" so, nor is it all that controversial at this point. Most of the complexity in descriptions is left over from the traditional, pre-computer methods used to calculate the date; in straightforward code, it's not that bad. As for the controversy, that was mostly settled in 325 AD. There is one remaining schism - between the Western and Eastern Orthodox congregations - and even they agree on the basic rule: Easter is the first Sunday after the first (approximated) full moon on or after March 21st. They only disagree in the choice of calendar, which leads to two discrepancies: the two calendars call different days "March 21st" (for years between 1900 and 2100, Eastern "March 21st" is the same day as Western "April 3rd"), and have slightly different rules for approximating the moon phases, so the calculated "full moon" falls on different dates between them. In 2012, Western churches will observe Easter Sunday on April 8th, but the Julian calculation places it on April 2nd, and because of the 13-day difference between the calendars, the actual date of Orthodox Easter is April 15th. --[[User:Markjreed|Markjreed]] 04:22, 4 June 2011 (UTC)
 
==Suggestion==
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::All of the easter holiday rules are catholic rules. But some of the dates required by the current task are dates when older versions of the rules were the "officially accepted versions". I would recommend, in addition to specifying the current catholic rules and the gregorian calendar, that we also change the task's example to use years from 1990 through 2020. --[[User:Rdm|Rdm]] 17:00, 9 July 2010 (UTC)
 
To take away the uncertainty, you only have to specify which set of rules. DifferentAs I said above, different churches use different rules (Gregorian, Julian, and maybe Revisedvs Julian), so you have to specify at least which of those you want. But having specified Gregorian, there's no need to limit it to such a narrow range of years; the Gregorian rules are valid in the Western Church as far back as the Gregorian calendar has been in use, which is of course locale-dependent, but goes back at least as far as 1929 everywhere (see [[wp:Gregorian Calendar#Adoption]]), and those rules are valid for the foreseeable future as well (though there have been proposals to abandon them in favor of a wholly astronomical calculation.) --[[User:Markjreed|Markjreed]] 03:58, 4 June 2011 (UTC)
 
Easter is defined relatively simply, albeit with an odd combination of factors: it's the first Sunday ''after'' the first full moon that occurs ''on or after'' the day of the Northern Hemisphere's vernal equinox. The devil is in the details. The traditional rules make use of approximations rather than accurate astronomical calculations; the details of the approximations changed between the Julian and Gregorian calendars; and the Eastern Orthodox Churches never adopted the Gregorian rules. In 2012, Western churches will observe Easter Sunday on April 8th, but the Julian calculation places it on April 2nd, and because of the 13-day difference between the calendars, the actual date of Orthodox Easter is April 15th. -[[User:Markjreed|Markjreed]] 03:58, 4 June 2011 (UTC)
Markjreed
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