Valentine's Day has been celebrated as a romantic holiday since the 14th century, although mid-February has been a traditional time to celebrate love and fertility for much longer. The exact origins of this holiday are actually somewhat unclear, and the situation is made more complicated by the fact that there are no less than three Saint Valentines, none of whom can be easily associated with love. The most accepted explanation for the origins of Valentine's Day is that it has its roots in pagan fertility festivals, which often took place at the close of winter.
In ancient times, many cultures celebrated a fertility festival in mid-February. In Rome, the festival came to be known as Lupercalia, and it included festive parades through the streets with an assortment of pagan symbols. During Lupercalia, men and women would draw tokens with random names on each of them to pair off for games and exchanges of gifts.
The Christian church frowned on the pagan and erotic nature of Lupercalia, and tried to institute a more staid festival to celebrate St. Valentine, although since all three Valentines were martyred on 14 February, it's unclear which one was meant to be celebrated. The practice of instituting a Saint's Day on a popular pagan holiday was quite common, so that converts could celebrate their new faith on traditional festival days. The question of which St. Valentine is meant to be celebrated cannot be resolved. One of the men cured the sick, another was imprisoned and tortured for his Christian beliefs, and the history of the third Saint Valentine is not known. Some scholars suspect that the first two are actually the same man, and in later years the myth that St. Valentine secretly married couples who were ineligible for matrimony was added.
Citizens were not terribly enthused about celebrating yet another Saint's Day, and Valentine's Day began to evolve into a celebration of love and marriage. The tradition of exchanging cards and tokens was continued, and during the height of courtly love, people began to select their own Valentine's mates. Couples exchanged Valentine's cards and gifts with each other, and Valentine's began to appear frequently in love poetry. The first written link of this day and love was provided by Chaucer, who wrote a love poem to commemorate the engagement of Richard II and Anne of Bohemia which linked the pairing off of birds with the royal engagement and Valentine's Day.
The elaborate exchanges of poetry, cards, and gifts on Valentine's Day cemented it as a holiday for the celebration of love in European popular culture. Valentine's Day has since spread all over the world, and many nations celebrate love on the 14th of February with flowers, gifts, and cards. It is one of the largest selling days for greeting card companies, as most lovers no longer make their own cards. In nations such as India where relationships between unmarried men and women are not encouraged, lovers often celebrate Valentine's Day secretly with stealthy meetings and gift exchanges.