Today holds a curious key to understanding the Christian calendar and the deeper meaning within it. Go with me here for a bit.
The march to Christmas (yes, Christmas) begins today with The Feast of the Annunciation. This is the day the Church celebrates the angel Gabriel coming to Mary and telling her she is with child.
Nine months from today will be Christmas. You may have heard that Christmas was selected by the early church to co-opt the Roman's winter solstice celebration.
That is an interesting legend but doesn't really hold up; for one thing, the solstice is December 21. The early Roman church likely set December 25 as Christmas after counting forward nine months from today, the Annunciation.
It gets even more complicated than that. There were great debates for centuries in the Church on when to set the date of Easter. The Feast of the Annunciation in some quarters marked the new year, and was related to the marking of Easter and the Spring equinox. There were some who insisted that Easter should coincide with the Jewish Passover. Others wanted to keep it on a fixed date; Easter began moving around the calendar, but the Annunciation and Christmas remained fixed.
A broader way of thinking of this is that the Annunciation, Easter and Christmas are connected to each other in an eternal cycle. Mary becomes pregnant, giving birth to Jesus nine months later; his life and ministry is marked in the days between Christmas and Easter. The day of her pregnancy is near to the day of his Resurrection, and so the cycle begins anew marking Jesus' conception, birth, life, death and new birth.
That makes the calendar a marker of incarnation. The calendar is a reminder that God dwells with us (or in the Greek, God "tents") with us in the person of Jesus, and he remains with us before and after the historic events of long ago. The calendar therefore becomes not just a keeper of days, but a method of prayer that, like the seasons, marks how new life leads to death that leads to new life.
In the sixth month the angel Gabriel was sent by God to a town in Galilee called Nazareth, to a virgin engaged to a man whose name was Joseph, of the house of David. The virgin's name was Mary. And he came to her and said, "Greetings, favored one! The Lord is with you." But she was much perplexed by his words and pondered what sort of greeting this might be. The angel said to her, "Do not be afraid, Mary, for you have found favor with God. And now, you will conceive in your womb and bear a son, and you will name him Jesus. He will be great, and will be called the Son of the Most High, and the Lord God will give to him the throne of his ancestor David. He will reign over the house of Jacob forever, and of his kingdom there will be no end."
Mary said to the angel, "How can this be, since I am a virgin?" The angel said to her, "The Holy Spirit will come upon you, and the power of the Most High will overshadow you; therefore the child to be born will be holy; he will be called Son of God. And now, your relative Elizabeth in her old age has also conceived a son; and this is the sixth month for her who was said to be barren. For nothing will be impossible with God." Then Mary said, "Here am I, the servant of the Lord; let it be with me according to your word." Then the angel departed from her.Luke 1: 26-38
If you want to know more about the development of the calendar, Thomas J. Talley, S.J., is considered the leading scholar on the topic. His books are a bit turgid but a goldmine of information.
Painting "The Annunciation" by Fra Angelico (1387-1455).