The Easter Triduum The Easter Triduum is its own Liturgical Season, just like Advent, Christmas, Lent, Easter, and Ordinary Time. The Word Triduum comes from Latin and means “Three days.” The Triduum begins at sunset on Holy Thursday and ends at sunset Easter Sunday. All liturgies offered during these three days are considered one continuous celebration, like acts in a play or a movie. So, by only joining for Easter Sunday, it is like showing up to the end of show without seeing the beginning or middle.