However, when the basis of his completion/"work" was God's commands, then they were complete as to his fiat. Further, it does not say six consecutive days, or have the following day stated as such or as the next day...the days are independently declared and relate to his command. So the six days stand based on fiat(s) but not necessarily on our conceived time frame. Only Gen. 1:3 speaks to immediacy all subsequent commands are directed at created matter...are they not. Genesis could very well read - "And God said, Let the land produce/bring forth living creatures, and there were living creatures" but what is clearly stated is "And God said, Let the land produce/bring forth living creatures...", no immediacy but rather agency/mediate. What was so? That God commanded the Land to produce...and it "was so" because his efficacious will is all sufficient.
Be that as it may, perhaps much more interesting to follow the thread relative to Theological implications as opposed to some "creation/evolution" conundrum...