Peter was quoting a Psalm 90:4 which says...
A thousand years in your sight
are like a day that has just gone by,
or like a watch in the night.
And means that a thousand years is a short time from the perspective of an eternal God, and was not intended to use as some kind of bible code to re calculate the creation week.
Also, it doesn't work when you pay attention to the fact that he says "the evening and the morning were the first day....etc"
Evening and Morning make it impossible to reinterpret as anything but... well... evening and morning.