The Heavenly Birthday of St Almachius, 1 January.
From the Roman Martyrology:
At Rome, St. Almachius, martyr, who, by the command of Alipius, governor of the city, was killed by the gladiators for saying, "Today is the Octave of our Lord's birth; put an end to the worship of idols, and abstain from unclean sacrifices."
Theodoret of Cyrus, The Ecclesiastical History
Book V, Chapter XXVI: Of Honorius the Emperor and Telemachus the monk.
"Honorius, who inherited the empire of Europe, put a stop to the gladitorial combats which had long been held at Rome. The occasion of his doing so arose from the following circumstance. A certain man of the name of Telemachus had embraced the ascetic life. He had set out from the East and for this reason had repaired to Rome. There, when the abominable spectacle was being exhibited, he went himself into the stadium, and stepping down into the arena, endeavoured to stop the men who were wielding their weapons against one another. The spectators of the slaughter were indignant, and inspired by the triad fury of the demon who delights in those bloody deeds, stoned the peacemaker to death.
When the admirable emperor was informed of this he numbered Telemachus in the number of victorius martyrs, and put an end to that impious spectacle."
The post on the Saint from Medieval Saints at Yahoo!
From Catholic Forum.
From Saints Alive.