But, beloved, be not ignorant of this one thing, that one day is with the Lord as a thousand years, and a thousand years as one day.
what is being said is
that one day (Gods time)
is with the Lord
as a thousand years (our time).
and a thousand years (our time)
is as one day (Gods time).
I have considered that the below might be the case.
one day of Gods time is as a thousand years
and each day of that thousand years is a thousand years of our time.
that would really be a long time.
because there would be
1 day (Gods time) = 365 x 1000 x 1000 = 365 million years (our time)
6 days (Gods time) = 2.1 billion years (our time)
God created the fish and the birds on the 5th day
which causes the above to fit in with the Cambrian explosion
that occurred apx 542 million years ago and lasted until
apx 485 million years ago.
and the 5th day ended in the Paleozoic era between
the mississippian and devonean period first amphibians and
that fits right in with the Bibles 5th day creations.
of course on the 6th day God created all the land animals and
then he created man and the 6th day began 365 million
years ago if the above is correct and lasted until adam
and eve were created and God rested on the 7th day and then they ate the forbidden fruit
and the recording of the time of man began.
https://en.wikipedia.org/wiki/Cambrian_explosion 
