Christmas is over, so why are 12 percent of the world’s Christians waiting until January 7 to celebrate? Orthodox Christmas is celebrated by approximately 260 million people worldwide, both in majority-Orthodox countries in Eastern Europe, like Russia and Greece, and in communities in Ethiopia, Egypt, and elsewhere.

(How Christmas has evolved over the centuries.)

Marked by devout vigils and traditional feasts, the holiday traces its origins back to the centuries-old decision of Orthodox churches to split from the Catholic church and adhere to a calendar that differs from the one used by most of the world today. Here’s what you need to know.

Disagreements as to when to officially recognize the birth of Jesus Christ stretch back all the