Editing Coptic calendar (section)

== Date of Easter ==
{{See also|Computus}}
The First Council of Nicaea (325) sent a letter to the Church of Alexandria stating "all our brethren in the East who formerly followed the custom of the Jews are henceforth to celebrate the said most sacred feast of Easter at the same time with the Romans and yourselves and all those who have observed Easter from the beginning."<ref>{{Cite book |editor1-last=Schaff |editor1-first=Philip |editor2-last=Wace |editor2-first=Henry |publication-date=1890 |title=The Synodal Letter |series=Nicene and Post-Nicene Fathers: Second Series |year=1986 |volume=14, The Seven Ecumenical Councils |pages=112–114 |place=[[Grand Rapids, Michigan]], U.S.A. |publisher=Eerdmans Pub Co. |isbn=0-8028-8129-7 |url=https://www.ccel.org/ccel/schaff/npnf214.vii.ix.html |access-date=2020-07-05 |archive-date=2021-01-17 |archive-url=https://web.archive.org/web/20210117202530/https://www.ccel.org/ccel/schaff/npnf214.vii.ix.html |url-status=live}} (http://www.tertullian.org/fathers2/NPNF2-14/Npnf2-14-27.htm {{Webarchive|url=https://web.archive.org/web/20200928145035/http://www.tertullian.org/fathers2/NPNF2-14/Npnf2-14-27.htm |date=2020-09-28 }})</ref>

At the Council of Nicaea, it became one of the duties of the [[patriarch of Alexandria]] to determine the dates of the Easter and to announce it to the other Christian churches.<ref>{{cite book |last=Declercq |first=Georges |title=Anno Domini: The Origins of the Christian Era |url=https://books.google.com/books?id=H8AZAAAAYAAJ |year=2000 |publisher=Isd |isbn=978-2-503-51050-7}}</ref> This duty fell on this officiate because of the erudition at Alexandria he could draw on. The rules to determine this are complex, but Easter is the first Sunday after a full moon occurring after the northern [[March equinox|vernal equinox]], which falls on or after 21 March in Alexandria. When [[Julius Caesar]] reformed the calendar, the northern vernal equinox was nominally on 25 March which was abandoned shortly after Nicaea. The reason for the observed discrepancy was all but ignored (the actual [[tropical year]] is not quite equal to the Julian year of 365{{frac|1|4}} days, so the date of the equinox keeps creeping back in the Julian calendar).

Between the Catholic Church and the Orthodox Church, there are different dates for holidays. In recent years there have been multiple attempts to [[Reform of the date of Easter|unify these dates]]. Some people are skeptical about the success of these attempts. Eastern Orthodox use the Julian calendar while Catholics use the Gregorian calendar. [[Pope Tawadros II of Alexandria|Pope Tawadros]], the Coptic pope, and [[Pope Francis]], the Catholic pope, agreed to the proposal to celebrate Easter on the same day. Pope Tawadros suggested to celebrate Easter on the second Sunday of April.<ref>{{Cite web |date=2015-10-25 |title=Popes Francis and Tawadros agree one Easter for all |url=https://en.wataninet.com/coptic-affairs-coptic-affairs/church-affairs/popes-francis-and-tawadros-agree-one-easter-for-all/14914/ |access-date=2023-05-27 |website=Watani |language=en-US}}</ref>