Advent is the liturgical season devoted to preparation for the coming of Christ at Christmas.
During this time the faithful are admonished
"When the Church celebrates the liturgy of Advent each year, she makes present this ancient expectancy of the Messiah, for by sharing in the long preparation for the Savior's first coming, the faithful renew their ardent desire for his second coming." CCC524
First Sunday of Advent November 28, 2021
Gaudete Sunday December 12, 2021
Christmas Day December 25, 2021
* Unless otherwise noted, all text is taken in whole or part from the Catechism of the Catholic Church Glossary ©2000
also excerpted from http://www.newadvent.org/cathen/01165a.htm