To get a picture of why Valentines day is so special, lets look at the Saint.
The first representation of Saint Valentine appeared in the Nurenberg Chronicles (1493); alongside the woodcut portrait of Valentine, the text states that he was a Roman priest martyred during the reign of Claudius known as Claudius Gothicus. He was arrested and imprisoned upon being caught marrying Christian couples and otherwise aiding Christians who were at the time being persecuted by Claudius in Rome. Helping Christians at this time was considered a crime. Claudius took a liking to this prisoner – until Valentinus tried to convert the Emperor – whereupon this priest was condemned to death. He was beaten with clubs and stoned; when that failed to kill him, he was beheaded outside the Flaminian Gate
Various dates are given for the martyrdom or martyrdom’s: 269, 270, or 273.