God rested on the seventh day, and set it apart for man to observe in honor of His creation of the heavens and the earth in six literal days. He blessed and sanctified and made holy the day of rest. When men are so careful to search and dig to see in regard to the precise period of time, we are to say, God made His Sabbath for a round world; and when the seventh day comes to us in that round world, controlled by the sun that rules the day, it is the time in all countries and lands to observe the Sabbath. In the countries where there is no sunset for months, and again no sunrise for months, the period of time will be calculated by records kept.... 3SM 317.1
The Lord accepts all the obedience of every creature He has made, according to the circumstances of time in the sun-rising and sun-setting world.... The Sabbath was made for a round world, and therefore obedience is required of the people that are in perfect consistency with the Lord's created world.—Letter 167, 1900. 3SM 317.2