Christmas Eve is the evening or day before Christmas Day and is observed as a full or partial holiday in anticipation of Christmas Day.
Christmas celebrations often begin on the night of the 24th, due in part to the Christian liturgical day starting at sunset, a practice inherited from Jewish tradition and based on the story of Creation in the Book of Genesis: "And there was evening, and there was morning – the first day." Since tradition holds that Jesus was born at night, Midnight Mass is celebrated on Christmas Eve, traditionally at midnight, in commemoration of his birth.
During the Reformation many Protestants changed the gift bringer to the Christ Child or Christkindl, and the date of giving gifts changed from December 6 to Christmas Eve.
In many parts of the world gifts are exchanged on Christmas Eve, rather than Christmas Day. In Spain, gifts are traditionally opened on the morning of January 6, Epiphany day.