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:
All Commentaries on Genesis 1:14 Go To Genesis 1
Augustine of Hippo
AD 430
We should not interpret the signs as something other than times. For Scripture is now speaking of these times that by their distinct intervals convey to us that eternity remains immutable above them so that time might appear as a sign, that is, as a vestige of eternity. Likewise, when it adds, “and for days and for years,” it shows of what times it is speaking. These days come about by the revolution of the fixed stars, and from this it becomes obvious when the sun completes its starry course in a particular year.