Typically the Church assigns dates for particular feast days. Sometimes it's on a Saint's death day/martyr day, other time it's on their birthday. September 8th is chosen because it's exactly 9 months after December 8th, the feast of the Immaculate Conception, meaning the day that Mary was conceived.
You're probably going to ask, "Well how do we know when she was conceived?! Where is that in the Bible?!?!"
Tradition and historical evidence shows that the feast of her birthday was celebrated before the feast of her conception. So the conception date was worked backwards from her birth date to figure out roughly when it was. Obviously not all pregnancies are exactly 9 months, but 9 months is just a simple starting point. That's it.
Yes I know, I'm explaining why it's September 8th, because it's 9 months after December 8th, the feast of the Immaculate Conception. That's the reason.
How do we know its today?
Typically the Church assigns dates for particular feast days. Sometimes it's on a Saint's death day/martyr day, other time it's on their birthday. September 8th is chosen because it's exactly 9 months after December 8th, the feast of the Immaculate Conception, meaning the day that Mary was conceived.
You're probably going to ask, "Well how do we know when she was conceived?! Where is that in the Bible?!?!"
Tradition and historical evidence shows that the feast of her birthday was celebrated before the feast of her conception. So the conception date was worked backwards from her birth date to figure out roughly when it was. Obviously not all pregnancies are exactly 9 months, but 9 months is just a simple starting point. That's it.
I took birthday to mean the day Mary was born, as you do.
Yes I know, I'm explaining why it's September 8th, because it's 9 months after December 8th, the feast of the Immaculate Conception. That's the reason.