This is not the feast of St Valentine as many people think. Ss Cyril and Methodius were two brothers born in Greece in the 820s and who went to eastern Europe, among the Slavonic peoples of Hungary and Slovakia, and preached the gospel.
They were centuries ahead of their time in their thinking in that they realised that to preach the gospel properly to people they had to speak in the language that the people understood.
To this end they translated the Bible into the local language and developed the Cyrillic alphabet to write the words down.
Jesus did the same sort of thing. He used every day things like sheep, farming, the weather, in order to teach the people.
To hear the gospel properly people must hear it in a language that they understand, be that farming, music, reading words or whatever.
What language shall you use today as you preach the gospel with your life?