A "day" also has a lot in common with an "age", or "era", etc, which is why I think seven "days" was a very good way of explaining to all of them an entire creations "day" or "age" or "era" from each of their very beginnings, all the way to their full, and final, and complete endings, etc.
We can barely comprehend what I am saying right now, and most definitely can't without a knowledge of a lot of other things first, most of which were just recently discovered most recently, in these last few centuries, or ages, or days, or eras, etc.
We label "ages" by what primarily dominated them, or took place in them most recently, etc. Well, it is no different with God in the creation account, etc. Day/age 5, the era or age of the sea animals, etc. Day or age 6, the era or age of land animals (including man close to the end of it, etc). Day 7 has not happened yet, but we know it will be the day/age/era of Jesus Christ's earthly paradise kingdom rule and reign on earth, and will at first consist of those taking part in the first resurrection, and after the first judgement, at the end of Armageddon, etc, or at the end or closing of the 6th day, or age, or era, etc.
And it will be the time of God in the OT's rest, etc. Until the very end of that 7th or last "day", when will be the second and very final resurrection and judgement, which some call the "white throne judgement", etc, when those from the first resurrection and judgement, will join those from the second resurrection or judgement, and will all be judged together in one final, last judgement, etc. When this whole entire creation, this lesser heaven, and his lesser earth, etc, will be all "melted with fervent heat" and will come to a final end, etc.
When, at that time, all will give up all their dead, and will join those from the first and second and last resurrection, for one very final last judgement, etc. When some will go to be with God the Father in the Highest Heaven to be there permanently after that, and to be with Him forever after that, and then some "not", or they will go into the lake of fire after that, or will have their memories erased/wiped, and be made to play their exact same role again, but in a newly started, or newly created, lesser heaven and earth, all over again, etc.
But only for as long as, and when their number comes back up again, etc. And this will be forever, just as it has always been from forever for them, but will not ever be so again for those who went on to be with God the Highest Father in the Highest Heaven ever again, etc. But those ones will be joined by others like them again at the very end of a very final and last day of a whole entire new other creation (lesser heaven and lesser earth) again, etc.
God Bless.