Who Celebrates Christmas In January? Where? Why?

Merry Christmas with green tabletop tree. Photo by Angela Lansbury. Copyright.

Problem
I have trouble remember which calendar and which countries celebrate in January and whether it's the 6th or 5th or 7th. Please explain - and make it easy to remember.

Answers
Julius Caesar landed in the UK BC. (Never mind accuracy and controversy - we just want the general easy to remember view.)

From him we get our first calendar, the Julian calendar. Julius Caesar, lived before Jesus. His month, July, occurs before Christmas.

Eventually the seasons got out of sync with the calendar.

Later, long after Jesus, along comes Christianity to the Romans, and a Christian Pope, Pope Gregory, who suggest a new calendar (in around 1582 - but no need to remember when).

If you stuck with the old calendar, events are later. The date of Jesus' birth falls in January.

Different countries were faster or slower to adopted the new, Gregorian calendar which we all follow. Many of the traditional, Orthodox, countries kept the old calendar for Christian festivals (just like Jews and Moslems use a different, lunar calendar so the festivals are on different dates each year).

Who celebrates Christmas eve on December 24th and Christmas Day on December 25th?

UK (and former British Empire - now Commonwealth, including New Zealand, Singapore, South Africa, Czech Republic.)
USA

January 7th
Russiand and adjacent Ukraine.
In alphabetical order:
Belarus, Egypt, Ehtiopia, Georgia, Kazakstan, Macedonia, Moldova, Montenegro, Serbia.

Author
Angela Lansbury, travel writer and photographer, author and speaker.