The concept of an annual Christian Calendar developed in an era of limited literacy. Both pictures (icons) and holy days (contracted to "holidays") were deemed helpful in sharing and reminding generally illiterate people of the Gospel story. Today the Bible is readily available in most languages and, in my view, more effective spiritual disciplines, such as a daily quiet time, are to be encouraged.

Yet in our era many literate people do not in fact commonly read, resulting in the Christian Calendar having again greater value. The Christian calendar begins with Advent in anticipation of the promise of Christmas. The point of Christmas on the Christian calendar is not that Jesus was born on any specific date, e.g. Dec 25 which is unknown, but that God was made flesh that we might know him and live forever with him:

Christmas as Cosmic Battle

If Christ had not come

Joyeux Noel

What about Santa Claus?

Candy cane