The real core of Christmas is nostalgia. It's wanting to believe there was a better time, because of course that allows us to believe there will be again a better time. So we're looking back to the perfect days of our childhood, or looking back to a perfect time of magic Christmases - Norman Rockwell's 1950s drawings, even though Rockwell himself looked back to the perfect Christmases of the 19th century, and in the 19th century people looked looked back to the perfect Christmases of the 16th century.