Eastern Orthodox Churches Celebrate Christmas on Different Dates

Calendar differences lead to varying observances, with some traditions marking the holiday on January 7th.

Certain Eastern Orthodox churches, including those in Russian and other traditions, celebrate Christmas on January 7th due to their adherence to the ancient Julian calendar, which runs 13 days later than the Gregorian calendar used by much of the world.
The Greek Orthodox tradition and some Ukrainian churches celebrate Christmas on December 25th, the same date as Western churches, following a revised Julian calendar that mirrors the Gregorian.
In Ukraine, the government declared December 25th to be Christmas as an assertion of national identity and cultural independence from Russia. The newer Orthodox Church of Ukraine observed Christmas on December 25th, while the Ukrainian Orthodox Church, which has historic ties to Moscow, is observing Christmas on January 7th.
In the United States, Christmas observances vary even within Orthodox traditions. Churches in the Greek and Antiochian traditions, along with the Orthodox Church in America, observed Christmas on December 25th. Some churches in the Slavic tradition, including Serbian and smaller Russian churches, will observe it on January 7th.
Eastern Orthodox Christmas traditions typically include a big worship service the night before Christmas. In Serbian Orthodox churches, worship often begins with a short outdoor ceremony involving the burning of an oak branch or young oak tree, accompanied by a proclamation of the birth of Christ.