Definitions for "Valentine's Day"
a day for the exchange of tokens of affection
Professor Lockhart decorated the walls in pink flowers, arranged for heart-shaped confetti to fall from the ceiling, and had dwarves in cupid costumes deliver cards and singing valentines (CS13); several years later Harry had his first real date with Cho Chang on Valentine's Day; they had coffee in Madame Puddifoot's tea shop, where golden cherubs hovered over the tables and occasionally threw pink confetti (OP25)
Saint Valentine's Day or Valentine's Day is on February 14. It is the traditional day on which lovers express their love for each other; sending Valentine's cards, candy, or donations to charities, often anonymously. It is very common to present flowers on Valentine's Day.