Advent Sunday, also called the First Sunday of Advent or First Advent Sunday, is the first day of the liturgical year in the Western Christian Churches and the start of the Christian season of Advent; a time of preparation for the celebration of Christ's birth at Christmas and the return of Christ at the Second Coming. Advent Sunday is the fourth Sunday before Christmas.
On the First Sunday of Advent, Christians start lighting their Advent wreaths, and praying their Advent daily devotional; believers may also erect their Chrismon tree, light a Christingle, as well as engage in other ways of preparing for Christmas, such as setting up Christmas decorations, a custom that is sometimes done liturgically through a hanging of the greens ceremony.