St. Augustine attempted three different times to explain the Hexaemeron in a literal sense, but each time he ended with an allegorical exegesis.
In 389 ("De Gen. c. Manich." in P. L., XXXIV, 173) he arrived at the conclusion that the cosmogonic evening and morning denote the completion and the inception of each successive work.
In 393 ("De Gen. ad lit. lib. imperf." in P. L., XXXIV, 221) the great African Doctor starts again with a literal explanation of Gen., i, but is soon perplexed by the questions: Did God consume the whole day in creating the various works? -- How could there be days before there were heavenly luminaries? -- How could there be light before the existence of the sun and the stars? -- This leads him to adopt simultaneous creation, to identify the light of the first day with the angels, and to explain the evening and morning by the limitation and the beauty of the various created objects.
In 401 Augustine began the third time to explain the Hexaemeron ("De Gen. ad lit. libr. XII" in P. L., XXXIV, 245; cf. "Retract.", II, 24; Confess.", lib. XII sq., in P. L., XXXII, 825), but published his results only fifteen years later. He admits again a simultaneous formation of the world, so that the six days indicate an order of dignity -- angels, the firmament, the earth, etc. Morning and evening he refers now to the knowledge of the angels, assuming that they denote respectively the angelic vision of things in the Word of God, and the vision of the objects themselves.
Thanks... that STILL wasn't what I was looking for, but it actually attacks the subject much more directly!