The scriptural content for this post is found in Genesis 1:1-5
In Genesis 1:3 God says "Let there be light.” When we read this we immediately understand that God is speaking about the physical light that He is allowing to pierce the darkness from space. What we may not immediately understand is that God is also speaking of the expression of His essential nature as light in the earth. This metaphorical use of the word light as God’s essential nature is certainly applicable here because God is directly expressing His divine nature through creativity on the darkened void of the earth. “Let there be light” describes the expression of physical light as a physical twenty four hour period on the physically darkened world. “Let there be Light” also describes the expression of God’s essential nature as spiritual light in shaping and creating the spiritually darkened world. The dark, void and formless world was not reflective of God's nature, intentions or purpose. It was God’s love in action or light that began to bring the earth into conformity with His nature.
For this reason we understand that the day described in Genesis 1:4-5 is of course describing the first physical twenty four hour earth day. We also understand that the days described in the entire creation narrative are describing an indeterminate period of God's creative light. Yes a physical earth day that God establishes in Genesis is an approximate twenty four hour period but the metaphorical days implied here could be any length of time.
The Hebrew word “yom” that is translated day in scripture is used much like we use the word day in English. When I speak of Abraham Lincoln's day we immediately understand that we are not speaking of a single twenty four hour period of time. Here in the creation narrative the metaphorical use of the word day is similar. Genesis chapter one reveals to us that God began the twenty four hour cycle of the earth day. Genesis chapter one also reveals that God began indeterminate, individual periods of the expression of his creative light. For this reason we know that the original earth day was approximately twenty four hours through simple scientific observation. We also understand that each day of the creation narrative, no matter how long that day was, is an individual period of the expression of a specific activity of God's creative light.