Here's what I have for my introduction for "The Cherry Tree Carol."

"In 1582, Pope Gregorius the 13th added 11 days to the calendar, because it had gotten out of alignment with the seasons. In 1752, England adopted this calendar. Some of the peasants refused to accept that the date of Christmas could be changed by the government, and so still celebrated it on the old date, January 6. Thus, it came to be known as "Old Christmas." It shows up in some older traditional songs, such as "The Wife of Usher's Well" and this one."

My thanks to all who posted. Mudcat is often an educational experience!