Back in ancient Rome they used to celebrate a young man’s entry into adulthood, or his rite of passage, during an event called the Fertility Festival which lasted several days and began on the 13th. On the first day the festival opened dedicated to peace and love. During the second day, February 14, the names of willing single women were placed into an urn and one was drawn by every young single man. These paired couples were partners for the following year which, on the Roman calendar began that March. Although there was no guarantee of commitment often these couplings, after a year of being together, would result in marriage.
In the fifth century the Christian church in its efforts to stamp out such pagan and sexual conduct created a coinciding holiday celebrating a Christian saint remembered for his devotion to love (Saint Valentine). They retained the idea of drawing names from an urn but instead of placing the names of willing women into the urn they placed the names of saints for young women and men to draw out and emulate for the following year. Needless to say this tradition was not nearly as popular as the former version. The new tradition also took away what was previously a great opportunity for a single male to find a partner, and visa versa. To make up for this single men began creating presents of written greetings of affection for girls they liked. They would present these on the 14th of February.
This tradition spread and evolved over the years so that during medieval times in England the names of single men and women were put into urns and drawn in pairs. Each couple would exchange gifts and be sweethearts for a year in which the man was bound by honor to court and protect his sweetheart. This tradition was made official when King Henry VIII declared February 14, Saint Valentines Day. The old traditions and the new were thus combined to create the Valentines Day we know today, in which sweethearts give each other gifts like flowers or candy and declare their love.