The Episcopal Church does not mark this as a feast day, but the Church of Rome remembers Ancetus on April 17th. He was the tenth successor of Simon Peter and, with Polycarp (who is on our calendar), developed the formula for determining the date of Easter.
Enable us, we pray, almighty God, to proclaim the power of the risen Lord, that we, who have received the pledge of his gift, may come to possess all he gives when it is fully revealed. Through our Lord Jesus Christ, your Son, who lives and reigns with you in the unity of the Holy Spirit, one God, for ever and ever.