First we must remember that the dates of Christmas and St Stephen's Day are not chosen at random. We have good reason for celebrating the birth of our Lord on December 25th - the ancient belief that a great man died on the anniversary of his conception couple with widespread belief in the early Church that Christ was crucified on March 25th lead naturally to the date we have for Christmas; and details concerning dates contained with the infancy narrative of St Luke's Gospel gives credence to that being the correct day also.
The feast days of saints are usually set as near the date of their death as is practicable. This custom is more especially observed if it is possible to do so in the case of martyrs. The tradition has always been that St Stephen died near the end of the year in which Christ was crucified. This makes December 26th a very credible date for his martyrdom and certainly an appropriate one for his feast day.
But why do I speak of Divine Providence as opposed to coincidence being behind the closeness of the dates? It is because we as Christians are given a powerful lesson from the fact that the martyrdom of St Stephen falls hard on the heels of the Birth of our Lord in our liturgical calendar. The death of the martyr reminds us that the child who was born came into the world to die. This is made particularly evident by the many echoes of our Lord's Passion and death that there are in the account of St Stephen's death. The one following so closely after the other brings back into sharp focus the reason that Christ came into the world - not to create a cute cradle scene that would sweet upon our mantelpiece, but the power of Satan to destroy, as it has it has it in the Christmas carol. And he would do that by his suffering and death. And remembering St Stephen's death so soon after the Nativity reminds us of what we, as Christians in the world, are called to do - to give faithful witness to the Gospel message, speaking the truth whatever the personal cost to us, doing so even though we know it will cause some to hate us for it, and doing all this lovingly, prayerfully, and joyfully.
That it should be a mere coincidence that such a powerfully appropriate lesson to us should be found in the Church calendar is to stretch credulity. And yet, as I said, the dates we have for these two festivals were not chosen by some wise father of the Church for the purpose providing us with this lesson. That leaves only the hand of God. And why should we find it difficult to believe that his guiding hand is to be found in this? We believe, as St Stephen did, that he became man and died for our sins. Why should we not believe that he would not think it important to remind us of this, even at Christmas?