Today is the Second Day, and according to Fr. Alexander Schmemann of Blessed Memory, the earliest observance on this day was not that of the martyrdom of St. Stephen, but a celebration of the life of the Mother of Our Lord. This was, as I read him, the first Marian feast (the Synaxis of the Most-Holy Theotokos), apparently long before other Marian feasts appeared on the calendar. But I'm going to have look more deeply into this, because my recollection is that, for example, her "birthday" was celebrated very early in the Church's history. (That seems to be reflected in the Protevangelion of St. James. But I know next to nothing about that, too.)
In any event, light an extra candle before your icon/s of the Theotokos. From Western usage: Hail, Mary, full of grace: The Lord is with you. Blessed are you among women, and blessed is the fruit of your womb, Jesus.
HYMN OF PRAISE
The Synaxis of the Most-holy Theotokos
At the border between night and sunny day,
The dawn is rosy, pink and dewy.
The crimson dawn thou art, O Virgin given by God,
Precursor of the day, rosy and glorious.
Thou didst correct Eve and restore her to Paradise.
Do not withhold thy help from us sinners.
Israel crossed dry-shod over the Red Sea;
A cool spring flowed from the rock in the wilderness;
The bush burned but was not consumed-
As the dawn resembles the crimson eve,
So thou, O Virgin, dost resemble those foreshadowings.
O thou whom the Church calls the Mother of God,
Unknown to sin, not given to sin,
O Most-pure Mother of our Savior,
Because of thy purity thou wast chosen by God,
To bring down the Eternal Creator to earth.
That is why thou hast authority to pray for us,
And we have the joy of hymning and glorifying thee
I have written before about my sort-of-not-very-"Lutheran" view of the Theotokos, so I won't go over it again.
I will, however, note that the coincidence of two observances of martyrdom is not insignificant to the Christian proclamation: Mary was wounded by the suffering of her son and, undoubtedly, mourns the sacrifice of every one of her son's followings, beginning with Stephen. It is, I think, during Christmastide that the theology of the cross becomes easiest to explicate (especially when coupled with the Slaughter of the Innocents), and yet in my experience, it is during this season that such a theology is last in evidence. (I don't mean to invoke the memory of the "Sad Danes," but the shadow of the cross lies darkly across the manger -- if manger there was. And we ought not to forget it.)
It is our sublime joy (we are makarios) that the Word became flesh -- the divine became human in order that the human might become divine. But that happy exchange came and comes at a cost. Have we abandoned counting that cost, to the detriment of our ultimate well-being?
A most blessed Christmastide to you!