Modern standard Italian itself is heavily based on the Latin-derived Florentine Tuscan language. The Tuscan-based language that would eventually become modern standard Italian had been used in poetry and literature since at least the 12th century, and it first became widely known in Italy through the works of authors such as Dante Alighieri, Giovanni Boccaccio, Niccolò Machiavelli, and Petrarch. Dante's Florentine-Tuscan literary Italian thus became the language of the literate and upper class in Italy, and it spread throughout the peninsula as the lingua franca among the Italian educated class as well as Italian traveling merchants. The economic prowess and cultural and artistic importance of Tuscany in the Late Middle Ages and the Renaissance further encouraged the diffusion of the Florentine-Tuscan Italian throughout Italy and among the educated and powerful, though local and regional languages remained the main languages of the common people.
Since when has Giovanni Boccaccio been used in poetry and literature? 