Several reasons why I think the days in Genesis 1 are of 24 hour duration:
- Style is narrative. This is clear from just reading it, but technical analysis concurs.
- A study looking at the verb forms in Genesis 1 compared to other passages in Scripture show that the frequency of verb forms for poetry are similar and those for narrative are similar. Genesis 1 has a frequency of verb forms that is strongly in line with other narrative.
- The waw consecutive is a Hebraic form that gives a narrative a sequential flow. It is translated "and," though it is predominantly sequential in its 55 occurrences in Genesis 1: read "then."
And God said, "Let there be light," and there was light. And God saw that the light was good. And God separated the light from the darkness. God called the light "day(time)," and the darkness he called "night(time)." And there was evening and there was morning, one day. (Genesis 1:3-5)
Remember the Sabbath day, to keep it holy. 6 days you shall labor, and do all your work, but the 7th day is a Sabbath to the LORD your God. On it you shall not do any work, you, or your son, or your daughter, your male servant, or your female servant, or your livestock, or the sojourner who is within your gates. For in 6 days the LORD made heaven and earth, the sea, and all that is in them, and rested on the 7th day. Therefore the LORD blessed the Sabbath day and made it holy. (Exodus 20)The reason this parallel is exact is because the word day is used. One can have a Sabbath of other time periods, usually years (Exodus 23, 2 Chronicles 36), but no comment is made about those periods being the same as the creation periods, ie. days.
In fact the existence of the week is a strong pointer to the literalism of Genesis 1. Day, month and year all have astronomical events that define them. Other time divisions are clearly a division or multiplication of these 3 fundamental periods. Decade and century from the decimal numerical scheme; seconds, minutes and hours from the sexagesimal scheme. The week is clearly a period based on days that has no logical explanation other than divine decree.
For those who deny the days are 24 hours this needs explaining. And it is likely the proposed hermeneutic will be invoked because of a prior, extra-biblical commitment to an ancient earth.