Why Do People Celebrate Valentine's Day?

St. Valentine was a Saint of romantic causes, who lived some time during the third century. This great person supposedly agreed to conduct marriages in secret, because the Emperor of Rome of the time, Claudius II, apparently banned marriages, because he felt that it was more likely for single men to enlist in the army, than it was for married men. St. Valentine however took matters into his own capable hands, and presided over secret marriages until February 4, 207, when he was found out and promptly executed.
Reportedly, St Valentine sent a note or a love poem to his jailer's blind daughter, just before his execution, signed, "From your Valentine". This became the catch phrase that we all use today; all across the globe, on Valentine's Day which falls on February 14th, when we wish to celebrate our romantic love for each other.