Jesus said, 'The Sabbath was made for man' (Mark 2:27). God didn't make the Sabbath for the earth; He made it for mankind - for you, for your neighbor, and for each person around the globe.
The fourth commandment enjoins the observance of 'the seventh day,' and all the inhabitants of our round world have a seventh day to each of their weeks. God has invited us to keep the seventh day as it comes to us and is marked off by His great time-keeper, the sun. When the sun sets on Friday night, we know that our six laboring days are past and that the Sabbath is commencing.
Read more of It's impossible to keep the Sabbath on a round earth.