Genesis 1:4-8

God saw that the light was good, and he separated the light from the darkness.

God called the light “day,” and he called the darkness “night.” So there was evening, and then the morning, making day one.

God said, “Let there be an expanse in the middle of the waters to divide the waters.”

So God made an expanse to divide the waters that were above from the waters that were below. And that's what happened.

God called the expanse, “sky.” So there was evening, and then the morning, making day two.