The actual length of the days in Genesis 1 has caused much controversy over past decades to the present day. The inception of modern secular science has fueled the debate with the invention of evolutionary theory – or all life on earth developing from a single organism – which by definition is claimed to have taken millions if not billions of years. It is right to accept the verses in Genesis 1 at face value. Although helpful, there’s no primary reason to examine the Hebrew meaning of the word “day” as used in Genesis 1 because the length of a day is defined within the text of the Creation account. The Genesis 1 text itself defines what a day is for us 6 times. Here’s one example:
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]
The remaining verses are as follows: Genesis 1:8, 1:13, 1:19, 1:23, 1:31
The length of a day is set by the spinning of the earth on its axis. This explains why God says there are days before He created the sun and the moon. The sun and the moon were created to govern what was already in existence – time. Let’s look at the text:
Gen 1:14-19 NASB Then God said, “Let there be lights in the expanse of the heavens to separate the day from the night, and let them be for signs and for seasons and for days and years;  and let them be for lights in the expanse of the heavens to give light on the earth”; and it was so.  God made the two great lights, the greater light to govern the day, and the lesser light to govern the night; He made the stars also.  God placed them in the expanse of the heavens to give light on the earth,  and to govern the day and the night, and to separate the light from the darkness; and God saw that it was good.  There was evening and there was morning, a fourth day.
TH!NK: What better proof of a literal 7, 24-hour per day Creation Week than our present 7, 24-hr per day week in which we currently live?