St Euphemia the Martyr is celebrated twice a year in the Orthodox Church…. on the 11th of July is the miracle of her relics that decided the 4th Ecumenical Council, held in Chalcedon, 451 AD…. the second Feast, on September 16th, celebrates her repose as a martyr. The Slavic tradition does not have a separate Sunday for the 4th Ecumenical Council, instead celebrating the Fathers of the first six Ecumenical Councils on that same Sunday.