Each year, on January 7, according to the Old calendar. That's December 25, only by the Old calendar, the Julian calendar. My own Serbian Orthodox Church, much like our brothers and sisters in Bulgaria and Russia, still use the Old calendar, instead of a new one: Julian, not a Gregorian, but even some Orthodox Churches already use the New calendar, like the Greek Orthodox Church, or the Romanian Orthodox Church.

Your customs sound very interesting 😊

I actually celebrate it twice in December.

Most Ukrainians also celebrate Christmas in January. Though last year they made the 25th of December day off, which is only fair, of course.

I'm from Croatia and as a Roman Catholic, I celebrate Christmas according to the new, Gregorian calendar, much like all the Christians in Western churches, unlike most Eastern Orthodox Christians, even in my own country. Who knows, maybe someday the entire Christianity would unite and accept the Gregorian calendar at last, so that we could all finally celebrate Christmas together as one, on a same day, on December 25. Now it looks like Jesus has not 1, but 2 birthdays: December 25 in the West and January 7 in the East. I think there should be only 1 birthday of our Savior, Jesus Christ, not 2! This is so confusing! In my hometown of Zagreb, much like the rest of Croatia, all the Orthodox Christians from a Serbian Orthodox Church celebrate Christmas in January. There should be only 1 Christmas all over the world, not 2, if you ask me.