Editing Old Calendarists (section)

=== Background ===
Until 1924, the [[Eastern Orthodox Church]] universally used the [[Julian calendar]], whereas the [[Roman Catholic Church]], under [[Pope Gregory XIII]], conducted a [[calendar reform]] resulting in the [[Gregorian calendar]] in 1582. The [[Gregorian calendar#Difference between Gregorian and Julian calendar dates|difference between the two calendars]] is 13 days between 1900 and 2100.<ref>{{Cite news|last=Anderson|first=L. V.|date=2013-01-07|title=Merry (Russian Orthodox) Christmas!|language=en-US|work=Slate|url=http://www.slate.com/articles/news_and_politics/explainer/2013/01/russian_christmas_date_why_do_eastern_orthodox_christians_celebrate_christmas.html|access-date=2018-02-18|issn=1091-2339}}</ref>

==== 1923 Congress ====
{{See also|New Calendarists}}
In May 1923, the [[Pan-Orthodox Council of Constantinople]], called by Patriarch [[Meletius IV of Constantinople]], adopted the [[Revised Julian calendar]]. This new calendar was different to the Julian calendar, and would not diverge from the [[Gregorian calendar]] for a further 800 years. The Revised Julian calendar replaced the tabular date of [[Easter]] of the Julian calendar with an [[astronomical]] date of Easter. The astronomical Easter was unpopular and hardly used at all, and for the purpose of calculating the date of Easter the Julian calendar was restored. Not all Eastern Orthodox churches were represented at the congress or adopted its decisions, and the [[Russian Orthodox Church]] and some other Eastern Orthodox churches have continued to use the Julian calendar liturgically to this day.