III. When is the Liturgy Celebrated?
Catechism number 1173
When the Church keeps the memorials of martyrs and other saints during the annual cycle, she proclaims the Paschal mystery in those "who have suffered and have been glorified with Christ. She proposes them to the faithful as examples who draw all men to the Father through Christ, and through their merits she begs for God's favors."45
The Liturgy of the Hours