1:5 one day. God established the pattern of creation in 7 days which constituted a complete week. “Day” can refer to: 1) the light portion of a 24 hour period (1:5, 14); 2) an extended period of time (2:4); or 3) the 24 hour period which basically refers to a full rotation of the earth on its axis, called evening and morning. This cannot mean an age, but only a day, reckoned by the Jews from sunset to sunset (vv. 8, 13, 19, 23, 31). “Day” with numerical adjectives in Hebrew always refers to a 24 hour period. Comparing the order of the week in Ex 20:8–11 with the creation week confirms this understanding of the time element. Such a cycle of light and dark means that the earth was rotating on its axis, so that there was a source of light on one side of the earth, though the sun was not yet created (v. 16).
1:5 called. God shows He is ruler of the cosmos by naming its spheres (17:5; cf. Num. 32:38; 2 Kin. 23:34; 24:17). By His creative commands and designations, God gave existence and meaning to everything according to His eternal counsel. For God Himself there are no mysteries, and all creation has coherence and meaning within His will. For man, the beginning of wisdom is the fear of the all-wise God (Prov. 1:7).
first day. This presentation of the creation week enables God’s covenant people to imitate the Creator in their weekly pattern of work and rest (Ex. 20:11; 31:13, 17).
Reformed scholars have proposed several interpretations of the creative “day.” Some view these as literal, sequential, 24-hour days. This interpretation usually entails the view that the earth is relatively “young” (c. 10,000 years old or less). Other scholars, noting that the Hebrew word for “day” (yom) can refer to periods of time (e.g., 2:4), have proposed the “day-age theory,” that the creative “days” refer to extended ages or epochs of time. Still others suggest that literal, 24-hour days are intended, but that these days were separated by extended periods of time. Finally, some scholars argue that the “days” of creation constitute a literary framework (vv. 3–31 note) designed to teach that God alone is the creator of an orderly universe, and to call upon human beings made in the image of the creator God to reflect God’s creative activity in their own pattern of labor (2:2; Ex. 31:17). This “framework hypothesis” views the days of creation as God’s gracious accommodation to the limitations of human knowledge—an expression of the infinite Creator’s work in terms understandable to finite and frail human beings. This last group of scholars observes that the universe gives the appearance of great antiquity, that the phrase “morning and evening” seems inconsistent with the “day-age” theory, and that the notion of intervening ages between isolated 24-hour days is not apparent from the text.
 MacArthur, J. F., Jr. (2006). The MacArthur study Bible: New American Standard Bible. (Ge 1:5). Nashville, TN: Thomas Nelson Publishers.
 Sproul, R. C. (Ed.). (2005). The Reformation Study Bible: English Standard Version (p. 7). Orlando, FL; Lake Mary, FL: Ligonier Ministries.