The associations we now have with the day came in the time of Chaucer*, the late 14th century, and it lingered on in english culture and literature. Shakespeare has Ophelia sing in Hamlet IV.v. 48-51:
To-morrow is Saint Valentine’s day,But in the thoroughly, orthodox tradition, eroticism has nothing to do with Valentine. Valentine is not Eros or Cupid. The love of Valentine† was agape. The same love of Christ, that, Christ had for man, and mankind; the love we are enjoined to have for each other. It is a fine, and of course, valiant name...why, my own father’s father was a Valentin.
All in the morning betime,
And I a maid at your window,
To be your Valentine.
Since writing this, I have attended mass to-day. The priest, before mass, said he would like to be the first to wish us a Happy Cyril & Methodius Day, and went on to say the calendar has changed, and the day is primarily commemorated to the two brothers, that evangelised the slavs. He went on to mention, that, the last pope (who wrote an encyclical epistle, Slavorum Apostoli, in 1985), and the current have wanted the unification of the east and west, and this is a fitting prayer on this day.
I have seen the BBC write on to-day, yesterday, that Valentine is not the right patron for the heart lonely, but Saint Raphaël. The archangel Raphaël brought Sarah and Tobias together. There was an error to their writing, what they referred to ‘as legend’ is Scripture.
* For this was on seynt Valentynes day,
Whan every foul cometh ther to chese his make,
― lines 309-10. The Parliament of Fowles c.1380.