The Breakdown: From the Source
Day 1: In the beginning, God created the heavens and the earth, and the earth was formless, empty [and dark]. And God said, “Let there be light,” and there was light.
If you attribute this passage to the birth of the sun and the subsequent accretion of planets, this happened 4.6 billion years ago.
Day 2: And God said,“Let there be an expanse between the waters to separate water from water.”
It’s thought that the earth cooled down enough to allow for the formation of liquid water and an atmosphere around 4.1 billion years ago.
Day 3: And God said, “…let dry ground appear.”
Uh, that’s, that’s pretty much the same as day 2.
And God said, “Let the land produce vegetation: seed—bearing plants and trees on the land that bear fruit with seed in it, according to their various kinds.”
Plants first appeared on Earth in primitive forms just prior to the fertile Carboniferous period, approximately 390 million years ago. Interestingly, prokaryotes appeared 3.5 billion years ago, with the earliest evidence of true photosynthesis at t minus, say, 3 billion.
Day 4: And God said, “Let there be lights in the expanse of the sky to separate the day from the night, and let them serve as signs to mark seasons and days and years”
What we already covered this. (4.1 billion years ago)
Day 5: And God said, “Let the water teem with living creatures, and let birds fly above the earth across the expanse of the sky.”
OH MY GOD (sic) the first sea creatures (e.g., arthropods) appeared EARLIER THAN PLANTS: 500 million years ago. Reptiles 300 million; birds 150 million.
Day 6: And God said, “Let the land produce living creatures according to their kinds,”
…which I am going to go ahead and assume means mammals, at 200 million years…
Then God said, “Let us make man in our image…”
Being Australopithically generous, let’s say 4 million years ago. Homo sapiens? 2.3.
The Math: Day Length
Day 1: 500,000,000 years.
Day 2: Oops, no real progress. We can go with 250,000,000 y each for 1 and 2.
Day 3: 1,100,000,000 years for photosynthetic prokaryotes;
2,700,000,000 years for true plants:
Average: 1,900,000,000 years.
Day 4: Oh I can’t even. See below. 792,000,000.
Day 5 (Day 3 average – Day 5 average):1,584,000,000. Factor in Day 4, whatever, just, whatever: 792,000,000 years.
Day 6: 789,000,000 years.
Day 7: Since there is no clear trend for day-length (refer to chart), the best one can do is to average Days 1 through 6, which equals 796,000,000 years.
We are currently in year 2,400,000 since the end of Day 6, as determined by the creation of man. Therefore, God is pretty much going to be straight-up resting for the next 793,600,000 years.