The Nouvelle Biographie Generale gives May 8 as his birthday.
This is a mere assumption, for Boccaccio only says generally May. The indication which Dante himself gives that he was born when the sun was in Gemini would give a range from about the middle of May to about the middle of June, so that the 8th is certainly too early. This is the date given by Boccaccio, who is generally followed, though he makes a blunder in saying, sedendo Urbano quarto nella cattedra di San Pietro, for Urban died in October, 1264.
Some, misled by an error in a few of the early manuscript copies of the Divina Commedia, would have him born five years earlier, in 1260.
According to Arrivabene,
Secolo di Dante, Udine edition of 1828, Vol.
III. Part I. p. 578. Sansovino was the first to confirm Boccaccio's statement by the authority of the poet himself, basing his argument on the first verse of the Inferno,—
Nel mezzo del cammin di nostra vita; the average age of man having been declared by