"The holy Hieromartyr Mocius, who was of Roman parents, lived during the reign of Diocletian, and was a priest in Amphilopolis of Thrace. One day as the idolaters were assembled, and the Proconsul Laodicius was offering sacrifice to Dionysius, Mocius entered the temple and overturned the altar. After many torments, through which he was preserved whole by grace divine, he was sent to Byzantium, where he was beheaded about the year 288. Saint Constantine the Great built a magnificent church in honour of Saint Mocius in Constantinople, where his holy relics were enshrined. He is one of the Holy Unmercenaries." (Great Horologion)
  The Prologue and St Herman Calendar give the date of his repose as 295.