God called the light day, and the darkness He called night. And there was evening and there was morning, one day. (Gen 1:5 NASB)
Since each creative day ends with the expression “there was evening and there was morning” is this an indication that they were 24 hours in length?
Regarding this verse the NICOT states:
The fact that evening is placed before morning throughout this chapter is not a foolproof indication that the OT reckons a day from sunset to sunset. There is some evidence that strongly suggests that the day was considered to begin in the morning at sunrise. For example, this view is supported by the fact that when the OT refers to a second day the time reference is the morning (Gen_19:33-34; Jdg_6:38; Jdg_21:4). Similarly, the phrase “day and night” is much more frequent than “night and day.” [A verse such as Lev_23:32, dealing with Day of Atonement observance, calls for the keeping of the sacred day on “the evening of the ninth day of the month, from this evening to the next evening.” This verse does not indicate a sunset-to-sunset reckoning, but rather the fact that certain sacred festivals are to be held also on the night of the preceding day.] Thus it seems likely that this refrain in Genesis refers not to the computation of a day but rather to the “vacant time till the morning, the end of a day and the beginning of the next work.” [R. de Vaux, Ancient Israel, 2 vols., tr. J. McHugh (New York: McGraw-Hill, repr. 1965), 1:181. See also U. Cassuto, A Commentary on the Book of Genesis, 2 vols., tr. I. Abrahams (Jerusalem: Magnes, 1961–1964), 1:28–30.] (The New International Commentary on the Old Testament)
If you read Genesis chapter 1 carefully, all of Jehovah’s creative activity, aside from the creation of light in verse 3, took place during the daylight. Nothing is said to have been created during the night. The expression “there came to be evening and there came to be morning” occurs after each period of activity during the light. Hence, it would be logical to conclude, as the NICOT comments, that “evening and morning” refers to the end of a day and the beginning of the next work.
The question I ask myself is, by this, did Jehovah mean to convey that his work of creation was confined to the daylight as if he needed light to see? The answer is an obvious no. So why does the account use expressions that appear to make it so? I think we have to remember that, although inspired, the Bible is written by humans with limited knowledge for humans with limited knowledge. God chose to relay information in a way that they could grasp at the time. That is why certain anthropomorphic expressions are made about God when in reality he does not have eyes, hands, ears, mouth and is neither male nor female. The Bible described the sun as if it travels in the sky at a time when humans were not aware that in reality it is the earth that rotates. He could have chosen to make this information known at the time but obviously preferred to allow humans to discover and learn this on their own. Not having this knowledge did not put them in any danger. Nor did it affect their ability to have faith in him as creator. Therefore, I believe the same can be said about the creation account. In Moses time, men usually accomplished work from sunrise to sunset. Jehovah allowed Moses to use this language to describe his creative process without seeing the need to give a science lesson about the actual length of time. This is my present understanding. But I am open to learning more as knowledge increases.
A good question to ask is what actually happened when God said: “Let light come to be”? (Gen. 1:3)