Saint Valentine was canonized on February 14, 496 AD by Pope Gelasius. Catholic lore states that Saint Valentine was a holy priest in Rome who was arrested for opposing Claudius' rule, and then executed for refusing to denounce his faith.
In reality, the origins of Saint Valentine are murky, and all that is really known about the man is that he existed. And, although Catholics made him the patron saint of love and happy marriages, they did not invent the romantic holiday. It is believed that Chaucer, medieval English poet, invented the holiday. Chaucer wrote a poem around 1375 that linked romantic gestures with February 14, which in the poem was a day for humans and birds to come together and find a mate. The celebration of Saint Valentine's feast day received widespread attention after Chaucer's poem.