And God called the light Day, and the darkness he called Night. And the evening and the morning were the first day.
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Basil the Great
Since the birth of the sun, the light that it diffuses in the air, when shining on our hemisphere, is day; and the shadow produced by its disappearance is night. But at that time it was not after the movement of the sun, but following this primitive light spread abroad in the air or withdrawn in a measure determined by God, that day came and was followed by night.