What does Genesis 1:13 mean?

This simple verse repeats the pattern for numbering each day of God's creation week. As mentioned previously, the Israelites counted days from sunset to sunset, from evening through morning and on into the daylight hours. That may be why each day is described in this way.

This completes the pattern of Genesis chapter 1, for the first half of the creation "week." In each case, God speaks, then His words are fulfilled, then He names His creation, and then declares it good. The Bible then applies a number to that creative day. Each of the first three days produced the conditions needed to support what God will create in each of the second three days. The first half of these days produced light, the sky and seas, and then land. The second half, then, will see God populate those areas with the sun and moon, birds and sea creatures, and land creatures, respectively.

The lack of detail in these verses is probably deliberate. The point of Genesis chapter 1 is to deliver a powerful truth: that God, and God alone, is responsible for the creation we see around us. And, that those created things have no power. Sun, sea, trees, and sky are not gods or spirits, but objects formed by God. We may not have complete understanding of how God accomplished His creation, but the Bible leaves no room for doubt as to who is responsible, and who has authority over what has been created.