In Judaism the Sabbath begins at sundown on Friday and extends until sundown on Saturday. Christians originally celebrated the Sabbath and the Lord’s Day, the day of Resurrection, on Sunday. Those two practices merged over time, as Gentiles (non-Jews) became followers of Jesus.
Sabbath, for Christians, is primarily Sunday and is to be a day dedicated to God in worship, rest, family time, even unplugging from the rest of the world. But any day or period of time can be taken as time to practice an intentional Sabbath for renewal, refreshment – physical, emotional, and spiritual. ~ VGM+