Herman Bavinck explains the days of creation in a very thought-provoking way (convincing, in my opinion). He says they were six days of “extraordinary character” (Reformed Dogmatics, II.499) Note: “triduum” means 3 day period.
“The first triduum…is formed and calculated in the biblical story in a way that differs from the second triduum. The essence of a day and night does not consist in their duration (shorter or longer) but in the alteration of light and darkness, as Genesis 1:4 and 5a clearly teaches. In the case of the first triduum this alteration was not effected by the sun, which only made its appearance on the fourth day, but came about in a different way: by the emission and contraction of the light created in verse 3. If this is the case, the first three days, however much they may resemble our days, also differ significantly from them and hence were extraordinary cosmic days” (p. 499).
“It is not impossible that the second triduum still shared in this extraordinary character as well. For while it is true that the sun and the moon and the stars were created on the fourth day, and it is conceivable therefore that the second triduum was determined by the rotation of the earth in relation to the sun, yet it does not follow that from the formation of the sun, the moon, and the stars on the fourth day astronomical and terrestrial relations were the same then as they are now. Scripture itself shows us that as a result of the fall and the flood cataclysmic changes occurred, not only in the human and animal world, but also in the earth and its atmosphere; and the period of creation in the nature of the case existed in very different circumstances from those that prevailed after the completion of creation” (p. 499-500).
Moses and the other “ancients” didn’t measure a day scientifically by minutes like we do, but by the presence and absence of light (morning/evening). Think about the extraordinary “day” (yom) in Joshua 10. Though it is a tough miracle to explain, one clear thing is that the “day” (yom) was measured by the presence and absence of light, not by a 24 hour time clock (Josh 10.13-14 & 27-28). Though it wasn’t literally 24 hours (it was probably quite a bit longer), it was still a literal day (yom).
Bavinck ends this great section with these words.
“The creation was a series of awesome miracles that the biblical story, which is both sublime and simple, portrays to us each time with a single brush stroke without giving details (p. 500).” “The days of Genesis 1 […] – like the days of creation as a whole – have an extraordinary character” (p. 499).
“…’Day’ in the first chapter of the Bible denotes the time in which God was at work creating. With every morning he brought into being a new world; evening began when he finished it. The creation days are the workdays of God. By a labor, resumed and renewed six times, he prepared the whole earth and transformed the chaos into a cosmos” (p. 500).
To me, this is more helpful than some of the other Christian descriptions of creation. I’m not a huge fan of the framework position or the gap theory, and some of the young-earth-literal-six-twenty-four-hour-day arguments go beyond Scripture, in my opinion. For me, Bavinck is one of the most level-headed, biblical, and careful commentators on the creation week. I encourage our readers to study this whole section of Bavinck (pages 495-500 of RD II) to see how he defends his position, which can be summarized like this: The triune God miraculously created all things out of nothing in six historical, extraordinary days.
I also like Galileo’s statement: In the Bible, “The Holy Spirit intended to teach us how to go to heaven, not how the heavens go.”