The date of his birth is not recorded, but hints in his writings suggest 1265. At the beginning of the Divine Comedy, the 1st part called Inferno, he says he was "midway on the journey of our life." If we assume the three-score years and ten of the Bible was considered typical, then he started when he was 35 years old. Since the Comedy (that's what he called it; Boccaccio tacked on the adjective later, and it stuck) was written in 1300, that would put his birth year at 1265. He also refers to himself as being born "revolved with the eternal twins," which suggests he was born under the astrological sign of Gemini. That puts his birthday between c.21 May and 20 June.
He was educated at religious schools, where he was introduced to much Italian poetry, and the writings of Cicero, Ovid, and Vergil.
When he was nine years old, he met Beatrice Portinari, the daughter of a banker, and fell in love at first sight. Despite whatever feelings he had for her, he was engaged at 12 to marry Gemma di Manetto Donati, of the powerful Donati family; they were wed probably in their early 20s, and had (we think) four children, of whom one, Jacopo, became a poet as well. Dante never wrote anything about his wife. Boccaccio, whose life overlapped Dante's, says his marriage brought him only trouble and pain.
A typical young Florentine Guelph, he fought for his province against Arezzo Ghibellines in the 1289 Battle of Campaldino. When the grandson of Charles I of Anjou, Charles Martel of Anjou, visited Florence in 1294, Dante was one of his escorts. Because a 1295 law required anyone aspiring to public office to be in one of the corporation of professions, he enrolled in the Apothecaries Guild. (Interestingly, books were sold from apothecary shops, so it seemed an appropriate choice for a poet and lover of poetry.) He held various small offices over the years.
The Guelphs (as opposed to the Ghibellines) were a group that supported the papacy. After the conflict mentioned above, however, the Guelphs split into two factions: White Guelphs (Dante's party) and Black Guelphs. The White Guelphs wanted more freedom from Rome, which became a problem for Dante, as I'll explain next time.