Millions of people around the world celebrated Orthodox Christmas on Wednesday, nearly two weeks after much of the world marked the holy day.
Certain Eastern Orthodox churches, including those in Russian and other traditions, follow the ancient Julian calendar. It runs 13 days later than the Gregorian calendar, used by Catholic and Protestant churches as well as by much of the secular world for everyday use.
The Ethiopian Orthodox Church and some other Oriental Orthodox churches — which are distinct from Eastern Orthodox but share many traditions — also celebrated Christmas on Wednesday.
Other Eastern Orthodox, including those in the Greek tradition, celebrate Christmas on the same Dec. 25 date as Catholic and Protestant churches.
The disagreement over when Dec. 25 actually falls
Most Orthodox agree that Dec. 25 is the date of Christmas, or the Feast of the Nativity, as they call it. The question is whether Dec. 25 falls on Dec. 25 or Jan. 7.
That requires a little unpacking.
The ancient church in the Roman Empire set its religious feasts based on the Julian calendar, but after more than a millennium, that calendar had increasingly gotten out of alignment with the solar year.