St. George (or sant Jordi in Catalan) is the patron saint of Catalonia.
La diada de Sant Jordi also known as el dia de la rosa (The Day of the Rose) or el dia del llibre (The Day of the Book) is a Catalan holiday celebrated on April 23 similar to Valentine's Day.
The gifts are exchanged between sweethearts - a rose to the woman, a book to the man. This day is also called "the Day of Lovers".

The roses are given in memory of St Jordi, who rescued a princess from the dragon he slew. The blood spilt from the dragon grew into a rose that Jordi gave to the rescued princess, a symbol of love.
Roses have been associated with this day since mediaeval times, but the giving of books is a more recent marketing ploy.
It started from 1923 when a Barcelona bookseller started the custom to help sell books, using as a hook the death date of two famous great writers on 23rd April 1616:
Spain's Miguel Cervantes, author of Don Quixote, and England's William Shakespeare.