Bishop William Millsaps researched this riddle and wrote the following answer.
"The Coptic and Abyssinian Churches are ancient parts of the Christian Church. They don’t mind witnessing to the rest of Christendom about the fact that the mother of our Lord is important and is a type of the obedience, which Christians ought to emulate. In the whole of Christian calendar there are only three birthdays celebrated. The days we call by the names of saints are the days they died. Many of them are, of course, martyrs. But some like St. Francis of Assisi and St. Patrick died of natural causes. What we celebrate in the case of all “the saints” is their heavenly birthday. The three earthly birthdays which have been kept by the majority of Christians for most of the Church’s life are St. John the Baptist, the Blessed Virgin Mary, and Christmas itself. It is sad to note that a poll I read about, taken a few years ago, found that most American children when asked whose birthday is celebrated on Christmas answered “Santa Claus.” You may doubt the accuracy of this poll, but all of us know all too well that it is a hard battle to focus on the Nativity of our Lord when the malls and parades are shouting another message.
"Maybe the Copts and the Abyssinians have something to teach us. They celebrate the birthday of Mary on the first day of every month. They also dedicate the month of May to special honors for her. The rest of the ancient churches keep September 8th as her birthday. I have been unable to find out why this day was selected. Perhaps you know and can tell me. I do know that this tradition was established by the seventh century.
"Our neighbors to the south in Mexico have a lot to teach us about love of family. When I was a boy we had the bracero program. You were allowed to bring farm workers from Mexico. I rode with my father in a truck all the way from Mississippi to Mexico. The men who came back to work for a short season were without doubt extraordinary. I was fascinated by their medals of the Virgin Mary, and the respect they had for her Son. I learned from them about the “Virgin of the Remedies.” When Cortez conquered the Aztecs he destroyed all the natives’ religious images. There is a wonderful legend about what happened next. There was found missing a little wooden Virgin and Child among the Spanish soldiers. Who knows why the natives were drawn to it? But good catholics that they were, the Spanish soldiers let the natives alone, when they found it missing. There had been enough killing. Over the centuries many stories were told about healings and other miracles connected to the primitive little statue. By the time of the Mexican Revolution in 1810 there was enough secular spirit that the victorious side seized the jewels and gold that had been laid at the feet of the little figure, and almost destroyed the church which had stood for centuries. But the first week of September is still the week of the Fiesta of the Virgin of the Remedies. Leading up to Mary’s birthday there is a celebration of hopes of good things. There is also a remembrance of good things, especially of the faith of parents and grandparents. Stories of faith abound. Twelve birthdays may be a bit much, but then again maybe not!"