The story of Stephen the deacon's killing and the persecution that followed it, some time in the first decade of the life of the infant church would have been told on the anniversary of his death for several more decades before Luke recorded it in his Acts of the Apostles. Another century would elapse before Luke's stories of the birth and infancy of Christ took their place in the evolving cycle of commemorations and story telling.
Nobody knew Jesus' birth date, so celebrating his birth was a matter of choice. Dates selected related to the winter solstice pagan festivities (25th) in the north of Europe and the celebration of the birth of Osiris (6th Jan) in Mediterranean lands. It was a way to 'baptize' the ancient impulse to feast in the quietest season of the year when little else could be done apart from wait for the arrival of better growing and working conditions. In due course both dates were universally adopted as well as the days in between, spanning the arrival of the new year, a festive season in honour of the incarnation of the Son of God.
This innovation did not displace the Feast of Stephen however, because it was already there from the earliest time in the collective memory of the church. He was the first of multitudes to die for their open profession of faith in Jesus Christ, and the difference they believed this would make to the destiny of humankind. Stephen's affirmation was perceived as a blasphemous innovation threatening the status quo of privilege and power as much as core shared beliefs.
His death was a traumatic set-back for the infant Christian community. Believers scattered far and wide, but they took with them a story which they couldn't help but tell to anyone that would listen. This was when they discovered that it could touch hearts and minds, inspire and change lives, and raise up new disciples among those who hadn't even heard of Jesus before.
Luke's account of Stephen's martyrdom echoes that of the death of Jesus. He looks up into the Beyond as he faces condemnation and he forgives his murderers as he is dying. The power of the Spirit bestowed upon Jesus' disciples enables them to behave like him, in loving compassion, self sacrifical service and willingness to suffer for the truth.
The wonder recalled in the moment of Christ's birth doesn't linger long as an exalted sentiment, but is rooted in the grim realities of a world where great fear has yet to be overwhelmed totally by great joy.