When is Mary’s birthday, and how do we know that’s the date?

The birthday of Mary has been celebrated by Christians since at least the sixth century. Though no one knows the real date of Mary’s birth, it has traditionally been celebrated on September 8th. It’s believed that September 8th was chosen because of its proximity to the Byzantine New Year on September 1st (the birth of the mother of the Savior represents the start of a new era, thus it made symbolic sense to have it close to the start of the New Year).