Genesis 1:5 And God called the light Day, and the darkness he called Night. And the evening and the morning were the first day.
And God said, Let there be lights in the firmament of the heaven to divide the day from the night; and let them be for signs, and for seasons, and for days, and years: So there was no sun to mark the days until the fourth "day". Thus, it is clear the "days" referenced here are not literal.