Final answer:
Advent is the first season in the liturgical calendar, marking the start of the Christian church year and a time of preparation for Christmas.
Step-by-step explanation:
The season that comes first in the liturgical calendar is Advent. This season marks the beginning of the liturgical year in the Christian church and starts on the fourth Sunday before Christmas Day, leading up to the celebration of the birth of Jesus Christ at Christmas.
The season of Advent is a time of preparation and anticipation for the coming of Christ, both in remembrance of the Nativity and in expectation of the second coming of Christ.