Catechism of the Catholic Church §349 — excerpt
The eighth day. But for us a new day has dawned: the day of Christ's Resurrection. the seventh day completes the first creation. the eighth day begins the new creation.
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: Roman Missal, Easter Vigil 24, prayer after the first reading