Advent begins on a Sunday between the dates of November 27 and December 3. Since Advent always starts on a Sunday, the specific date varies from year to year but always falls within the specified range.
Advent is the period of preparation leading up to Christmas. It includes the four Sundays leading up to Christmas Day. Counting back four Sundays, starting with the one immediately before Christmas, is an easy way to calculate the start date of Advent for a particular year. In the Catholic religion, the start of Advent is defined as the Sunday closest to the feast of St. Andrew the Apostle, which falls on November 30.