The Feast of Saint Valentine was established on February 14 in 496 AD by
Pope Gelasius in honor of
Saint Valentine of Rome who was martyred in 269 AD, about 50 years before Christianity became tolerated and then the official religion of the Roman empire.
Saint Valentine's Day become connected with romantic love in the 1300's and 1400's with ideas of "
courtly love", "
lovebirds" in early spring, etc.
In the 1700's in England it became a time when couples expressed their love for each other with gifts and other tokens of love such as cards, candy, etc.