And God said, "Let there be lights in the dome of the sky to separate the day from the night; and let them be for signs and for seasons and for days and years, and let them be lights in the dome of the sky to give light upon the earth."  And it was so.  God made the two great lights - the greater light to rule the day and the lesser light to rule the night - and the stars.  Got set them in the dome of the sky to give light upon the earth, to rule over the day and over the night, and to separate the light from the darkness.  And God saw that it was good.  And there was evening and there was morning, the fourth day.
Genesis 1:14-19 (NRSV)