The problem with all the discussion about what is meant by a "day" is that even if it were somehow possible to travel back in time (and it isn't possible, in spite of a bunch of good science fiction stories), one could not travel past any of these major continuities and assume that the clock that you had with you would still measure time as it actually was then. You cannot apply current measures of time to what transpired on the prior side of each major discontinuity.
This is a major problem for evolutionary theory. It presumes a uniform time line and attempts to fit all the fossil evidence into it. But the time line is not uniform, and we really have no way to even define, let alone measure, how time transpired back then.
Denying the uniformitarian hypothesis is the pulling out of the table cloth underneath the whole house of evolutionary cards.
So how do we make sense of Gen 1? It is not an eyewitness narative of the actual event, but a revelation by God after the event. It cannot possibly be anything else. As a revelation, I take it as reasonable that it is structured as a sort of thematic outline and summary of what transpired. The structure of seven days is purposeful mainly for teaching us the lesson that time, as well as space, matter, and energy, is a creation of God, and that by counting our time in seven day increments and resting on the seventh we do acknowledge and honor God as the creator and Lord over time, including our time. How long did it actually take God? I have no idea -- He could have done it in an instant or in bilions of years, and we have no meaningful way to measure that would make any distinction between the two.
Good God (no pun intended), not another Velikovskian! You folks breed in the dark?