Orthodox Christmas will be observed on January 7, by millions of Christians across Eastern Europe, Africa, and the Middle East. While much of the world celebrates Christmas on December 25, Orthodox Christians follow a different liturgical calendar, making their celebration fall 13 days later... The difference in dates arises from the use of two calendars. Most Western Christian churches follow the Gregorian calendar, introduced by Pope Gregory XIII in 1582 to correct inaccuracies in the older Julian calendar. This reform fixed the date of Christmas as December 25. However, many Orthodox churches chose not to adopt the Gregorian calendar for...