To place “St.” before “Valentine’s Day” or leave it off — that is the question. You’ll see it both ways on calendars, ads and so on.
It seems to be up to the writer these days. This writer prefers acknowledging at least in passing the religious aspects of the holiday (holy day). I am reminded by the “Saint” or “St.” as well as the apostrophe in “Valentine’s” that there is a person and a history behind the holiday we devote to love. I think it is appropriate, but that’s just me.
The reality is that in our modern American culture St. Valentine’s Day, along with many other holy days, is no longer much of a religious holiday. Feb. 14 is just a place on the calendar to gather with loved ones in a mostly secular celebration.