Shlama Akhi Ivan,
Yes, that is true. And before that we switched to the Julian Calendar from the Semitic (lunar) calendar.
In fact, the early Church of the East did not celebrate Christmas at all. It rather celebrated the Epiphany on Jan. 7th. To this day, in fact, "Christmas" is a rather unimportant day (liturgically speaking.) It is "Easter" that is much more important liturgically.
Ah, the western innovations have not escaped us entirely ... <!-- s
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+Shamasha
PS - a schismatic group, the "Ancient Church of the East", split in 1968 partly over this issue. They continue to celebrate "Easter" according to the Julian Calendar (which, to my amusement, they call "the old calendar" <!-- s
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