What is the liturgical season before Christmas?

Advent.

It is a time of hope, of joyful anticipation.It is an eschatological time.

It is not a time of penitence. Some people get confused by this since both Advent and Lent call for Violet vestments. To help distinguish the nature of these two periods, liturgists have suggested wearing a more purple-violet during Lent and penitential seasons, and more of a blue-violet during Advent.

Advent begins on the Sunday closest to the feast of St. Andrew (November 30). Since he was the first called of the apostles, it was deemed fitting that the Sunday near his feast mark the beginning of the (western) Liturgical Year, and of the time of expectation for the coming of Christ.