In the Acts of the Apostles, observance of the Old Covenant sabbath was not one of the requirements enjoined on gentile Christians by the Council of Jerusalem with the words “It seemed good to the Holy Spirit and to us...”
The first day of the week (Sunday in English, but called Kyriake — the Lord’s Day — in Greek) is the commemoration of Our Lord’s Resurrection, to which the Synaxarion for Pascha informs us the Holy Apostles transferred the dignity of the sabbath. Of course, the last day of the week is still called Sabbaton in Greek, and like Sunday is a day when the Divine Liturgy may be served in the midst of Great Lent, when otherwise the Liturgy is not served, and also like Sunday has fasting lightened with a katalysis (for oil and wine, or for fish, oil and wine, depending on the fast) so the Old Covenant sabbath persists in a lighter form along with the observance of Sunday as the Lord’s Day, at least in the Christian East.
In the Acts of the Apostles, observance of the Old Covenant sabbath was not one of the requirements enjoined on gentile Christians by the Council of Jerusalem with the words “It seemed good to the Holy Spirit and to us...”