The Saint of the day for December 18th is Saint Gaitian, bishop.
Saint Gatian (also known as Gatianus) came from Rome with Saint Dionysius of Paris, about the middle of the third century, and preached the faith principally at Tours in Gaul, where he fixed his episcopal see. The Gauls in that part were extremely addicted to the worship of their idols. But no contradictions or sufferings were able to discourage or daunt this true apostle; and by perseverance he gained several to Christ. He assembled his little flock in grots and caves, and there celebrated the divine mysteries. For he was obliged often to lie hid in lurking holes a long time together in order to escape a cruel death, with which the pagans frequently threatened him, and which he was always ready to receive with joy if he had fallen into their hands. Having continued his labors with unwearied zeal, despite frequent sufferings and dangers for near the space of fifty years, he died in peace at Tours in 301, and was honored with miracles.