（单词翻译:单击）
No one really knows. What is known is that Christian1 leaders in 336 A.D. set the date to December 25 in an attempt to eclipse a popular pagan holiday in Rome (Saturnalia) that celebrated2 the winter solstice. Originally, the celebration of Christmas involved a simple mass, but over time Christmas has replaced a number of other holidays in many other countries, and a large number of traditions have been absorbed into the celebration in the process (as we will see in later sections).
