February 15 is the date of the Lupercalia, the better-known of two ancient Roman fertility festivals, honoring the god Lupercus. It followed the lesser-known Faunalia on February 13, which honored Faunus. The Romans considered Faunus and Lupercus closely related, and some historians think they are the same god under different names. The main center of the Lupercalia was the cave of the Lupercal on Rome's Palatine Hill, where Romulus and Remus were supposedly nursed by a she-wolf, and the festival's name derives from that wolf connection. Its rituals included two nearly naked young priests running around the old city walls and slapping bystanders with thongs cut from sacrificed animals, a smack believed to cure sterility, as well as a purification of Roman women by the priests of Pan Lyceus. The Lupercalia is regarded as the oldest of the Roman festivals and, with the Saturnalia, among the most significant. Two prominent noble families, the Fabius and Quinctilius, were charged with organizing it each year. It survived the arrival of Christianity until AD 494, when Pope Gelasius I replaced it with the Feast of the Purification. That feast was first observed on February 14, and the date was later filled with the two Saint Valentines. Valentine's Day is therefore an ancient pagan festival covered with a thin Christian veneer, and God's people do not keep it.

According to tradition, Nimrod's mother presented herself for purification on February 15, forty days after his believed birth date of January 6. On this date, pagan Rome celebrated a sensuous festival of idolatrous worship beginning the evening before on February 14, in honor of Lupercus, the deified hero-hunter of wolves, known as the Lupercalia. This festival encouraged young people to indulge in licentious acts of sexual immorality. In AD 496, Pope Gelasius officially Christianized the pagan Lupercalia by renaming it Saint Valentine's Day and moving the day of observance from February 15 to February 14. Roman church members were then to center their attention on Christian saints, drawing lots with saints' names instead of engaging in the original pagan practices.

February 15 was the day pagan Rome celebrated Lupercalia, a sensuous festival honoring Lupercus, the deified hero-hunter of wolves, beginning the evening before on February 14. The date traces back to Nimrod, whose birth was believed to be January 6; his mother, following custom, presented herself for purification forty days later, on February 15. On this day the priests, called Luperci, sacrificed goats and a dog, then ran a marked course around the city scantily clad in goatskin girdles, striking women with strips of goat skin called februa to remove their infertility. The word is connected with februare, meaning to purify, so the day was called Februatus and the month Februarius. The festival encouraged young people who were attracted to each other to indulge in sexual immorality, and it became tied to Venus and Cupid. Roman church leaders in the 5th century took in the popular festival, and in AD 496 Pope Gelasius Christianized it by renaming it St. Valentine's Day and moving its observance from the 15th to the 14th. The change was only cosmetic, since the day remained as pagan and popular as ever.