Catechism of the Catholic Church §1040 — excerpt
The Last Judgment will come when Christ returns in glory. Only the Father knows the day and the hour; only he determines the moment of its coming.
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.