A straightforward section for your consideration today. After the Gospel narratives (but before they were written) we have the witness of St Paul:
21. It was for this reason that, from Apostolic times, “the first day after the Sabbath”, the first day of the week, began to shape the rhythm of life for Christ’s disciples (cf. 1 Cor 16:2). “The first day after the Sabbath” was also the day upon which the faithful of Troas were gathered “for the breaking of bread”, when Paul bade them farewell and miraculously restored the young Eutychus to life (cf. Acts 20:7-12). The Book of Revelation gives evidence of the practice of calling the first day of the week “the Lord’s Day” (1:10).
Others noticed, as early as the second century after Christ:
This would now be a characteristic distinguishing Christians from the world around them. As early as the beginning of the second century, it was noted by Pliny the Younger, governor of Bithynia, in his report on the Christian practice “of gathering together on a set day before sunrise and singing among themselves a hymn to Christ as to a god”.(Epist. 10, 96, 7) And when Christians spoke of the “Lord’s Day”, they did so giving to this term the full sense of the Easter proclamation: “Jesus Christ is Lord” (Phil 2:11; cf. Acts 2:36; 1 Cor 12:3). Thus Christ was given the same title which the Septuagint used to translate what in the revelation of the Old Testament was the unutterable name of God: YHWH.
Jesus, to us Christians is both Christ and Lord (Dominus).
Catholic Sensibility 