Except that every day has 24 hours. That's what we refer to as a "day". You're caught up in this vision-dream thing. I'm not. To me Genesis is a chronological order of events. You think God created things at night? Does anyone think that? Why would nighttime be chosen to get things done?
"Evening and morning" is not 24 hours. "Evening to evening" would be 24 hours, or sunrise to sunrise would be 24 hours.
"Evening and morning" is a very peculiar and particular phrasing that is not seen anywhere else, not anywhere else in the bible or in extra-biblical sources. So, it's presumption to assert it means the same thing as the other ways a 24-hour day is referenced. It's expressed differently because it
means something different.
My theory of what happened:
I believe there was a man who was given vision-dreams over the course of six nights. We see in scripture that vision-dreams are a common way that God presents significant blocks of knowledge to people, both believers and unbelievers. And we see that very frequently, these vision-dreams are only scantly "narrated" by God, if narrated at all.
This is something that occurred to me a long time ago, back in the early 60s, in part having seen several nature films that featured time-lapse photography. If you've ever seen time-lapse photography of growing plants or other natural phenomena, changes seem to burst forth suddenly. For instance, a plant bursts suddenly from dry, lifeless dirt.
Most importantly, the person having the vision-dream does not have any kind of "Godlike" omniscient viewpoint. He sees what he's shown from a normal human viewpoint and with normal human understanding. He can't fly, he doesn't have microscopic vision or telescopic vision.
I think in this case, each dream encompassed a segment of Creation, but the real-time of those segments was not equal. Yet, each segment of Creation was contained in the vision-dream for that single night, six nights in a row.
So, if the writer of Genesis had been shown a billion years compressed like time-lapse photography into the vision of a single night, the changes would appear suddenly, almost instantaneously. And there would a lot of things happening that he would not perceive at all until they became visible from an earth-surface viewpoint through normal human vision.
So, then, on the first night of his visions, he would see nothing at all for some period, then suddenly only light. Most likely, that would be the sun reaching the temperature of casting visible light, but it would be filtered through thick, primordial clouds enveloping the earth. The sun and moon already exist, but they would not be visible as discrete disks of light through the heavy cloud cover. The cloud cover would be like a dense fog all the way to the surface of the earth, so the ground itself would not even be visible.
In the vision of the second night, the cloud cover lifts enough that the ground is distinguishable from the sky, like a dense, high fog.
In the vision of the third night, from the position of the dreamer, ground has risen, or water has begun flowing, and a separation of dry land and water is visible. Plant life has also developed to the point that it's visible to the naked eye.
In the vision of the fourth night, the cloud cover has cleared enough so that the sun and moon present discrete disks.
In the vision of the fifth night, animals have become visible to the naked eye. Remember, that with billions of years lapsed into the dream of a single night, these things will appear suddenly to the dreamer.
Then in the vision of the sixth night, the dreamer will see what he can recognize as man suddenly appear. There would be no dream on the seventh night...the story of God's initial creation ends at that point, and the spoken histories of specific individuals begin.