And then the next age/generation(Gen.2:4) would begin. But,,in the next generation there would still be an sin that would not be forgiven https://biblehub.com/matthew/12-32.htm .... So if the generations of the heavens and the earth are the 7 days of creation in Genesis 2:4 then "six days thou shalt labor...and on the 7th rest",,, so was it going from day/age/generation 3 to 4 or 5 to 6 or the 7th?
I think I see where you are going with this days of creation parallel, wherein Jesus (the sun of righteousness) 'enters the timeline in the fourth (ie, as would be appropriate to 'the door') day, and so also the moon (we the lesser light)?