Why is Orthodox Christmas celebrated 13 days after Dec. 25?

While much of the world has celebrated Christmas, people in some Eastern Orthodox traditions will do so Sunday.

Certain Eastern Orthodox churches, including those in Russian and other traditions, follow the ancient Julian calendar, which runs 13 days later than the Gregorian calendar, used by Catholic and Protestant churches.

Other Orthodox, including those in the Greek tradition and some Ukrainian churches, celebrate Christmas on the same date as Western churches.

WHY ARE THERE DIFFERENT DATES FOR CHRISTMAS?

Technically, there aren’t. All Eastern Orthodox agree that Dec. 25 is the date of Christmas. The question is whether Dec. 25 falls on Dec. 25 or Jan. 7.

The ancient church set its religious feasts based on the Julian calendar, but after more than a millennium, that calendar has increasingly gotten out of alignment with the solar year. Sixteenth century Pope Gregory XIII approved a more astronomically precise calendar which bears his name. It abruptly shifted the calendar several days forward to make up for lost time and added a more precise calculation of leap years. Protestant churches eventually followed the Catholic lead in adopting the calendar, as did secular governments.

Eventually, most churches adopted a revised Julian calendar that mirrors the Gregorian.

But the Russian Orthodox Church has kept to the old calendar, observing Christmas on Jan. 7 on the new calendar, as have Serbian, Georgian and some other Orthodox.

WHAT ABOUT NORTH AMERICA?

Churches in the Greek and Antiochian traditions, along with the Orthodox Church in America, observed Christmas on Dec. 25. Some churches in the Slavic tradition will observe it Jan. 7.

In the small American Carpatho-Russian Orthodox Diocese of North America parishes can choose their date. About a third are on the new calendar.