Among the saints who share this day with the great Cyril and Methodius and two martyrs named Valentine is St. Abraham of Harran.
St. Abraham was a hermit in Syria in the later 300s. Hearing of a poor pagan village in the Mt. Lebanon area, he left his solitude and went there to gain the village for Christ, setting himself up as a fruit dealer. The villagers really liked his high quality produce and honest low prices, but weren't so in love with his preaching, which they ran away from or poked fun at. Until the economy took a decided turn for the worse, and the empire's taxes came due, which none of the villagers had any money to pay.
They saw no hope, and were resigning themselves to inevitable dispossession and imprisonment, but Abraham, their crazy Christian fruit man, took out a loan and paid the taxes for the whole village. Thankful for being able to stay in their village and homes and out of prison, they were convinced that Christians were really good generous people, and might be worth listening to. In short order, the whole village was converted. Abraham stayed there for another three or four years, teaching, and working hard to pay off the loan, then he went back to his hermitage in the Syrian desert.
People from the village, then others who heard of him, went out to the desert to seek his spiritual counsel. One of those people was a young nobleman named Theodosius the Younger, who came out for regular spiritual guidance whenever he could absent himself from his noble duties. A big problem with having a highly-placed disciple is that one doesn't get to stay in one's desert hermitage --- Abraham was taken to be bishop of Harran in Mesopotamia. Despite his preference to go back to the desert, he was both holy and competent as a bishop, and the church at Harran thrived. When Theodosius became emperor, he kept Abraham as his spiritual director, and several times each year, Abraham went to Constantinople for his pastoral visits with the emperor. During one of these visits to the capital, Abraham died of natural causes, in the year 422.