Just a few quotes...
“For as Adam was told that in the day
he ate of the tree he would die, we know that he did not complete a thousand years. We have perceived, moreover, that the expression, 'The day of the Lord is as a thousand years,' is connected with this subject.”
Justin Martyr (Dialog with Typho the Jew chapter 81 [AD 155])
In this quote St. Justin Martyr speaks of the “day” in Genesis meaning a period of a thousand years by pointing out that despite God telling Adam he would die the day of sinning he lived over 900 years. That is to say that the days were not literal 24 hour periods. This view is not limited to St. Justin.
St Irenaeus expresses a similar idea;
“And there are some, again, who relegate the death of Adam to the thousandth year; for since "a day of the Lord is as a thousand years," he did not overstep the thousand years, but died within them, thus bearing out the sentence of his sin.”
(Against Herasies, 5:23 [AD 189])
It appears that this view of each day containing a thousand years was popular among Early Church Fathers as we read from St. Cyprian of Carthage:
“As the first seven days in the divine arrangement containing seven thousand of years, as the seven spirits and seven angels which stand and go in and out before the face of God, and the seven-branched lamp in the tabernacle of witness, and the seven golden candlesticks in the Apocalypse, and the seven columns in Solomon upon which Wisdom built her house l so here also the number seven of the brethren, embracing, in the quantity of their number, the seven churches, as likewise in the first book of Kings we read that the barren hath borne seven”
(Treatises 11:11 [A.D. 250])
Clement of Alexandria writes that we cannot know when creation took place from reading Scripture:
“That, then, we may be taught that the world was originated, and not suppose that God made it in time, prophecy adds: "This is the book of the generation: also of the things in them, when they were created in the day that God made heaven and earth." For the expression "when they were created" intimates an indefinite and dateless production. But the expression "in the day that God made," that is, in and by which God made "all things," and "without which not even one thing was made," points out the activity exerted by the Son. As David says, "This is the day which the Lord hath made; let us be glad and rejoice in it; " that is, in consequence of the knowledge imparted by Him, let us celebrate the divine festival; for the Word that throws light on things hidden, and by whom each created thing came into life and being, is called day."
(Miscellanies 6.16 [208 AD])
St. Augustine says the following of his view of the word “day” in the Creation Week.
“But simultaneously with time the world was made, if in the world's creation change and motion were created, as seems evident from the order of the first six or seven days. For in these days the morning and evening are counted, until, on the sixth day, all things which God then made were finished, and on the seventh the rest of God was mysteriously and sublimely signalized. What kind of days these were it is extremely difficult, or perhaps impossible for us to conceive, and how much more to say!”
(City of God 11:6 [AD 419])
As St Augustine refers to the days as “impossible to conceive”, it is doubtful that he has 24 hour days in mind, for they are aren't inconceivable, after all.
Though people claim that there is a universal consesus on interpreting Genesis amongst the Church Fathers, in reality that doesn't seem to be the case, at all.