Catechism of the Catholic Church §1163 — excerpt
"Holy Mother Church believes that she should celebrate the saving work of her divine Spouse in a sacred commemoration on certain days throughout the course of the year.
This translation is under copyright, so only the cited words are quoted here. Follow the link for the full text. Translation: English translation of the Catechism of the Catholic Church, 2nd ed. (Libreria Editrice Vaticana), as posted at vatican.va.
Also cites: SC 102