re: Why do you say that:
"Genesis clearly states that the Earth, seas and all plant life were created on the third day"
How would you explain to a primitive culture how the universe was formed?
They would not have any knowledge of words such as mass, space, and energy, but they would have an understanding of words such as, "heaven," "earth," and "spirit," would you not use their words to try and convey the meaning of space, mass, and energy?
Notice that Genesis 1:8, is the first time the word "Heaven" is spelled with a capital letter and it refers to the "firmament," so what is the "heaven" (spelled with a small "h") before and after that?
Also notice that Genesis 1:10 is the first time the capital "E" is used in the word "Earth", so what was the formless and void "earth" that was created "in the beginning"?
Could it be that the word "earth" represents something general and all inclusive, such as the word "mass" does today?
How about the words "heaven" and "space" do they have the same meaning?
Is a "spirited" person "energetic"?
I think that the various religions are the result of the different interpretations of what has been written down by the original writers.
Just something to think about.