Although we hear of months, seasons, and years in Paradise Lost, the crucial measure is diurnal. Used in more than one sense, “day” and “days” appear just over 150 times. Yet given the great differences of situation, locations, and characters to which a “day” may apply, its meaning, not its name, is one of the things for which we seek assurance. Our human time and plot in the fallen world are subjects of Michael's prophesies in 11 and 12 (see Excursus 12.553). Such human time is the history of Adam and Eve and their descendants after the final lines of the poem. In other words, the plot of the poem as it involves Adam and Eve entails an order of events not ordinarily accounted historical or, in strict terms, accessible to us. The very language available to human capacity may be inadequate. It is only with difficulty, if at all, that we comprehend a dating like “on such day / as Heav'ns great Year brings forth” (5.581– 83). There is no wonder therefore that establishing and dating events of the poem entail matters even more disputed than biblical history. (See Excursus 12.553.) For example, early Church authorities disagreed over the time span between Creation and fall. Yet for all the difficulties, or perhaps impossibilities, the chronology of the events in the poem itself holds a crucial role in our making sense of the poem.
Whether narrated as if in process (the Fall) or in retrospect (the War in Heaven), the great actions of the poem are related in terms of days. A fundamental issue concerns those “days.” Can we presume that the days of the Creation and the day of the Fall are “days” with the same meaning? If not, the logical alternatives are temporal units differing but understandable, units relative and more or less understandable in context, or units incalculable. This issue is one for which Milton provides some evidence, as for example in connection with the War in Heaven and the expulsion of the rebel angels.
Raphael both begins and ends his account of those events by suggesting that his narrative must be accommodated to human understanding. The necessity suggests that its true nature is above and different from human calculation. On the other hand, Milton goes out of his way to assure us of the adequacy of our comprehension (suitably accommodated to be sure). The first of these speeches is Raphael's preface to his relation and is generally called the accommodation passage (5.570–76).
yet for thy good This is dispenc't, and what surmounts the reach Of human sense, I shall delineate so, By lik'ning spiritual to corporal forms, As may express them best, though what if Earth Be but the shaddow of Heav'n, and things therein Each to other like, more then on earth is thought?
The question that concludes is not simple, but seems to suggest that when heavenly matters are adapted for our understanding we can grasp them adequately. That assurance of adequacy of understanding events properly related seems to be the point of Raphael's concluding comment (6.893–96):
Thus measuring things in Heav'n by things on Earth At thy request, and that thou maist beware By what is past, to thee I have reveal'd What might have else to human Race bin hid.
Here, the purpose of the narration, warning Adam and Eve not to fall as the rebel angels did, presumes adequacy of understanding of those supernal things.
There are, however, other passages that imply modes of understanding different from those Raphael has employed. The first of these occurs near the beginning of the poem and tells of the nine days of stunned confusion the rebel angels weltered through in Hell (1.50–53).
Nine times the Space that measures Day and Night To mortal men, he with his horrid crew Lay vanquisht, rowling in the fiery Gulfe Confounded though immortal.
Mortal poet speaks to mortal readers about unaccommodated time as measured in our world. On the other hand, after the violent second day of battle in Heaven, God has words for the Son (6.684–87):
Second Omnipotence, two dayes are past, Two dayes, as we compute the dayes of Heav'n, Since Michael and his Powers went forth to tame These disobedient.