Though there are a number of Christians who question a literal interpretation of the creation week, a closer look at Genesis 1:1–2:3 should challenge those who have abandoned or are uncertain about the traditional understanding of the creation days. I will give four reasons to embrace a literal interpretation of the days in the creation week.
First, the Hebrew noun yôm, “day,” is used in our passage 14 times, 13 times in the singular and once in the plural (v. 14). It is used in the singular in Genesis 1:5 (twice), 8, 13, 14 (twice), 16, 18, 19, 23, 31; 2:2 (twice) and 2:3. The reason why this is significant is that yôm always refers to a normal literal day when it is used as a singular noun and is not part of a compound grammatical construction (such as the noun yôm being used with a preposition immediately attached to it or yôm being a part of the multi-word construction known as the construct-genitive relationship). And these 13 uses of yôm demand a literal day.
Second, Genesis 1:5 defines a day as a period of light separated from darkness: “God called the light Day, and the darkness he called Night. And there was evening and there was morning, the first day” (ESV). Clearly, this suggests we are dealing with normal literal days.
Third, each of the creation days has a numeric qualifier—“first day,” v. 5, “second day,” v. 8, etc. Excluding for the moment our passage (Gen 1:1–2:3), when yôm is used with a numerical qualifier in the Old Testament, it is not used in an extended, non-literal sense. The use of “day” with a number is clearly demonstrated in Numbers 7. In this context, leaders from each tribe of Israel brought various gifts to the Lord on twelve, sequential, literal days. A number qualifies each use of the word “day.” Numbers 7:12 illustrates this point, “He who offered his offering the first day was Nahshon the son of Amminadab, of the tribe of Judah” (for the remainder of the days along with their numerical qualifiers, see vv. 18, 24, 30, 36, 42, 48, 54, 60, 66, 72, 78). The sequential numbering of days is also found in Numbers 29:17–35. Thus, the use of “day” with a number is a clear reference to a literal day.
Fourth, because the word “day” in this context is qualified by “evening” and “morning,” each day is to be taken literally. The clauses in which these two nouns are found, “and there was evening and there was morning,” stand in juxtaposition with each enumerated day of the creation week (1:5, 8, 13, 19, 23, 31). Whenever “evening” and “morning” are used together in a context with “day” (19 times beyond the 6 uses in Genesis 1) or they appear together without “day” (38 times), they are used consistently in the Old Testament as a reference to literal days.
In conclusion, the use of “day” in the creation account unmistakably refers to normal 24-hour days. As John C. Whitcomb has observed: “It is difficult to imagine what more the Scriptures could say to convey the idea that the days of creation were literal days. ‘If it were not so, I would have told you’” (“The Science of Historical Geology in the Light of the Biblical Doctrine of a Mature Creation,” Westminster Theological Journal 36 [Fall 1973]: 68). For further information on this subject, see my journal article: “A Defense of Literal Days in the Creation Week.”