We know from the following verse, one of God days is as a thousand years.
Bible 2Peter 3.8 But beloved, be not ignorant of this one thing, that one day is as with the Lord as a thousand years, and a thousand years as one day.
Besides Genesis is clear on the matter of day being divided from night ,and it mentions seasons, days and years.
Genesis 1.14 And God said, Let there be lights in the firmament of the heaven to divide the day from the night; and let them be for signs, and for seasons, and for days, and years
The author of Genesis was focused on an entirely different point than was the author of 2 Peter. Attempting to use two different books by two different authors to make your case is like that (relatively) famous contradictory poem:
Ladies and gentlemen, hobos and tramps,
cross-eyed mosquitoes and bow-legged ants,
I stand before you to sit behind you
to tell you something I know nothing about.
Next Thursday, which is Good Friday,
there's a Mother's Day meeting for fathers only;
wear your best clothes if you haven't any.
Please come if you can't; if you can, stay at home.
Admission is free, pay at the door;
pull up a chair and sit on the floor.
It makes no difference where you sit,
the man in the gallery's sure to spit.
The show is over, but before you go,
let me tell you a story I don't really know.
One bright day in the middle of the night,
two dead boys got up to fight.
(The blind man went to see fair play;
the mute man went to shout "hooray!")
Back to back they faced each other,
drew their swords and shot each other.
A deaf policeman heard the noise,
and came and killed the two dead boys.
A paralyzed donkey passing by
kicked the blind man in the eye;
knocked him through a nine-inch wall,
into a dry ditch and drowned them all.
If you don't believe this lie is true,
ask the blind man; he saw it too,
through a knothole in a wooden brick wall.
And the man with no legs walked away.
What we want to study is what the author of Genesis wished to convey. Trying to turn this backwards into an entirely separate point being made by the writer of Peter is simply presenting us with an example of a backwards poem.