Hebrew writers commonly when writing would make a "blanket" statement, then 'back up' and give the detail. A good example of this is Adam and Eve. Genesis 1:27 states, "So God created man in his own image, in the image of God created he him; male and female created he them." The next chapter details how He did it (breathed into Adam's nostrils, took his rib, etc). God didn't create man twice; just declared it, then later gave more detail. This is the idea from the beginning of chapter 1. "In the beginning God created the heaven{s} and the earth." This is the 'blanket' statement. This is what He did in summary. Then, beginning in verse 3, we read the detail. Notice that each day begins with, "And God said...", and then explains all that He did that day. So day 1 would be represented in verses 3-5, Day and Night.