Much of what we know about Saint Valentine has been handed down through various legends and traditions. Saint Valentine was however listed in the Martyrologium Hieronymianum that was compiled in 460 AD of earlier writings. Pope Gelasius I set his feast day for February 14th in 496, writing that Saint Valentine was among those "... whose names are justly reverenced among men, but whose acts are known only to God."
One famous story tells that Saint Valentine was the Bishop of Terni, Narnia and Amelia was placed into house arrest with Judge Asterius. Saint Valentine struck up daily conversations with the judge in an attempt to convert him to the faith. One day, Jude Asterius devised a plan to prove or disprove the existence of God - he told Saint Valentine to restore sight to his blind daughter, and if he was successful he would do anything for him. Saint Valentine prayed before placing his hands over her eyes and miraculously she could see with no issue. For three days the Judge fasted and broke idols to the pagan gods he had in his house. He released all Christian prisoners and converted alongside his entire 44 person household.
Another story retold in the Nuremberg Chronicle, Saint Valentine as a priest was living in Rome and secretly marrying Christians - a serious crime under Emperor Claudius Gothicus (Claudius II) (In addition to marrying Christians, Saint Valentine was also accused of marrying them so that the husbands would not be drafted into the pagan army of Rome). Saint Valentine was also aiding Christians being persecuted in the city - another serious crime on top of the secret marriages he was performing. The emperor personally called for his arrest. When Saint Valentine was brought to Emperor Claudius, the emperor initially took a liking to the Saint and began to converse with him. The conversation, however, turned completely around when Saint Valentine began to persuade Emperor Claudius of the Christian faith. In a rage, Claudius ordered Saint Valentine's execution. Soldiers beat the Saint with clubs and stones before beheading him outside the Flaminian gate in 269 AD.
Today, Saint Valentine is still listed in the official Roman Martyrology. His feast day was listed as a simple feast until 1969 when the Roman Calendar was revised. The Eastern Orthodox Church celebrates Saint Valentine on two days - July 6 and July 30th. Saint Valentine's feast day likely became associated with romantic love in the middle ages with the writings of Geoffrey Chaucer.
Saint Valentine's skull with a crown of flowers is exhibited in the Basilica of Santa Maria in Cosmedin, Rome with his other remains laying at Saint Anton's church in Madrid.