origin: (1620) English; Christmas + Tidings (as in "Good Tidings").
DON'T THROW OUT THAT CHRISTMAS TREE JUST YET!!!
"The Christmas Season", which includes and extends beyond the actual holiday to just after New Years Day (often December 24 to January 6 - the baptism of Christ); the 12 days of Christmas separate from Advent. "Epiphanytide" marks the period after Christmastide with additional traditions ending in a cumulative celebration.
a.k.a. Your excuse to be late with cards & gifts (and perhaps take advantage of serious shopping discounts). However, to some, the word is also just another way of saying "Christmas", Christmastide can also be called "Twelvetide" -- an unbroken period of joy and celebration.
This practice began as Ancient Roman rulers was working out the kinks in its calendar and created a rest period for common workers. There are specific traditions associated with each day, such as the blessing of animals on the 2nd day, and the enjoyment of sacred wine on the 3rd, etc. Such traditions are celebrated around the world: from Europe, to Russia, to East India!