Only the Father knows the day or the hour because, while Jesus always had a divine nature, he set the glory of his divine nature aside. Paul tells us in his epistle to the Philippians: “…though he was in the form of God, [Jesus] did not count equality with God a thing to be grasped, but emptied himself, taking the form of a servant, being born in the likeness of men.” (Phil 2:6-7)
The *Catechism of the Catholic Church * explains: “[The] human soul that the Son of God assumed is endowed with a true human knowledge. As such, this knowledge could not in itself be unlimited: it was exercised in the historical conditions of his existence in space and time. This is why the Son of God could, when he became man, “increase in wisdom and in stature, and in favor with God and man,” and would even have to inquire for himself about what one in the human condition can learn only from experience." (CCC 472)