Garrison Keillor in his daily birthday list says:
Today is Valentine's Day, the day on which we celebrate love, especially romantic love. The holiday was named after an early Christian priest, St. Valentine [link to the History Today site] who was martyred on February 14 in 269 A.D. The tradition of exchanging love notes on Valentine's Day originates from the martyr Valentine himself. The legend maintains that due to a shortage of enlistments, Emperor Claudius II forbade single men to get married in an effort to bolster his struggling army. Seeing this act as a grave injustice, Valentine performed clandestine wedding rituals in defiance of the emperor. Valentine was discovered, imprisoned, and sentenced to death by beheading. While awaiting his fate in his cell, it is believed that Valentine fell in love with the daughter of a prison guard, who would come and visit him. On the day of his death, Valentine left a note for the young woman professing his undying devotion signed "Love from your Valentine".
This is a wonderful story. It would be murderous to kill it because of lack of evidence sufficient to convince 21st-century sceptics. What do you want after 1,744 years?
The saint was taken off the Catholic calendar in 1969! You go to the Catholic encyclopedia it waffles around about there being three different Valentines and implies that maybe they are all apocryphal. Wikipedia explains:
Several differing martyrologies have been added to later hagiographies that are unreliable. For these reasons this liturgical commemoration was not kept in the Catholic calendar of saints for universal liturgical veneration as revised in 1969.
Not good enough! Such a good story deserves to be retold and passed on as a matter of faith.
Meanwhile there is still hope for rehabilitating the saint:
The Martyr Valentinus who died on the 14th of February on the Via Flaminia close to the Milvian bridge in Rome" still remains in the list of officially recognized saints for local veneration. Saint Valentine's Church in Rome, built in 1960 for the needs of the Olympic Village, continues as a modern, well-visited parish church.