Western Christian Church, and is one of the most culturally significant celebrations in Christendom in the Western world.
The reason why celebrations start on Christmas Eve is that the traditional Christian liturgical day starts at sunset. This is an inheritance from Jewish tradition, which is based on the words in the Book of Genesis: "And there was evening, and there was morning – the first day."
Christians believe that Jesus was born at night, which is why Midnight Mass is celebrated on Christmas Eve, traditionally at midnight, in commemoration of his birth.
Christmas Eve is also referred to as "Heilige Nacht" ("Holy Night") in German, and "Nochebuena" ("the Good Night") in Spanish.