One of the reasons frequently given for why Genesis 1 shouldn’t be read literally is that the order of the creation days gives the creation of light before the creation of the sun and moon. How can it be that light existed before the heavenly bodies? How can one have an “evening and morning” without the sunrise and sunset? How can there be plants on the third day before the sun and moon on the fourth day? Here are a few quotes from John Calvin’s commentary on Genesis that address these questions:

Let there be light It be proper that the light, by means of which the world was to be adorned with such excellent beauty, should be first created; and this also was the commencement of the distinction, (among the creatures.) It did not, however, happen from inconsideration or by accident, that the light preceded the sun and the moon. To nothing are we more prone than to tie down the power of God to those instruments the agency of which he employs. The sun and moon supply us with light. And, according to our notions we so include this power to give light in them, that if they were taken away from the world, it would seem impossible for any light to remain. Therefore the Lord, by the very first order of creation, bears witness that he holds in his hand the light, which he is able to impart to us without the sun and moon.

And God called the light That is, God willed that there should be a regular vicissitude of days and nights; which also followed immediately when the first day was ended. For God removed the light from view, that night might be the commencement of another day.

Let the earth bring forth grass Moreover, it did not happen fortuitously, that herbs and trees were created before the sun and moon. We now see, indeed, that the earth is quickened by the sun to cause it to bring forth its fruits; nor was God ignorant of this law of nature, which he has since ordained; but in order that we might learn to refer all things to him he did not then make use of the sun or moon. He permits us to perceive the efficacy which he infuses into them, so far as he uses their instrumentality; but because we are wont to regard as part of their nature properties which they derive elsewhere, it was necessary that the vigor which they now seem to impart to the earth should be manifest before they were created.

The whole of the commentary on Genesis can be found here.