Catechism of the Catholic Church §1001 — excerpt
When? Definitively "at the last day," "at the end of the world." Indeed, the resurrection of the dead is closely associated with Christ's Parousia:
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: LG 48 # 3