Days run from midnight to midnight, right?
For Sundays and things like Christmas and Easter, the day starts the evening of the day before, on the “eve.” Which means the evening mass on Christmas Eve is a mass of Christmas Day (the first of four).
Christmas Eve pulls together all of Advent. Especially with the first two readings. The first reading rejoices as all the prophecies a brought to fulfillment. The second reading recalls God’s promise to David and the words of John the Baptist about the one to come after him.
And then? Then the Gospel bogs down in the genealogy of Jesus.
Why? To show how God's promise to David is being fulfilled in Jesus.
There’s a saying that “Behind every great man there’s a great woman.”
The Christmas Eve Gospel turns that upside down. Showing us the great man behind the great woman. And the silent “yes” to God behind the greatest “yes” to God.