When God began creating the heavens and the earth, he was kind of a newb. And frankly, it showed. At first, God made a kind of an earth, but it was without form. And, as you might already know, it was void, too. But really, those are fancy ways of saying the earth was a piece of shit. But the earth had something God called "the deep," and the deep was dark. To be honest, everything was dark. Whatever that deep dark was, it was part of the earth, so it was probably important.
The deep may have just been the water. There was water everywhere - and not just on the earth. Water was above the earth, too. In fact, the water reached all the way up into the sky. God called it "the waters," because "waters" sounds more spiritual than "water."
So God saw the water he created and he was all like, "Look at me! Blessed be the mother fucking waters, bitches!" and he blew his holy wind all over it.
The heavens? First, don't go getting your heathen panties in a wad just because I said "heavens" instead of "heaven." The plural "heavens" just means "some shit up there you don't understand." There's only one heaven, okay? It's where God, Jesus and Jerry Falwell are right now.
Before creation, God wasn't anywhere at all. He had to first make an anywhere so he could go to it and then be somewhere. So along with the earth, God made the heavens - heaven - so he could be there. Perhaps even more importantly, God could come from there and go back there.
At this point, it was still dark, so God thought up light. How cool is that? If you never saw light in your life, and if nobody was around to tell you what light was, you wouldn't know that it was dark or what your eyes were for or that you needed God to invent something like light. But God! God thought up the opposite of dark and said, "Let there be light," and there it was. Light! Now you could see shit.
The first shit God saw was that his light was good. That doesn't necessarily mean his darkness was bad, although darkness usually means bad. God was just saying that his light was good. In fact everything was good so far, except for the initial formless void incident. Nothing else was bad at all. God was on a roll, and it was good, so God created a word for it: "good."
If God hadn't created the word "good" he wouldn't have even needed to create the word "bad." There's no point in dwelling on it now. What's done is done. God created light and was so impressed with himself that he created the words "good" and "bad" so he could call the light good, and define "good" as "not bad."
If he was going to really prove that he made only good shit, God needed more than words. God needed some bad shit. Then, any time he wanted, God could point to the really bad shit and say, "My shit is good shit. See that shit over there? That's not my shit. That's bad shit."
So, the light was good shit and the darkness wasn't necessarily bad shit. God noticed, however, that light and darkness at the same time is just light. So God thought up "days" and in a brilliant moment of infinite fairness, he gave the light about half of every day while the darkness got the other half. The darkness would start each new day at evening, and the light would take over in the morning.
And that was the first day. It wasn't a thousand years or any nonsense like that. It was just a day.