You can't definitively say it's 7 24 hr days with God based on what Peter wrote. But a man with primitive technology might frame it that way to explain the world around him. If you're going to be that certain then why stop there? Should we follow Leviticus? Of course not. We're under the New Law. But you want to be legalistic.
Genesis one is not based on what Peter wrote. I don't care what man does with primitive technology. Do you need it? If so, why?Too much evidence that the days of creation were days of ordinary length. If the days were thousands or millions of years it would be a problem. In Genesis 1:16, two great lights were made, one to rule the day and the lesser to rule the night. Since these days were divided, according to Genesis 1:15 into “evening and morning” you ready to assume the sun came up but didn't go down for a few thousand or a few million years? There's another problem, if the “days” were eons of time, the plants were brought about on the third day of creation and the sun on the fourth day. Plants must have sunlight in order to produce their food through photosynthesis. Animals are dependent upon plants as a basic source of food. Plants and animals existing millions of years without the sun? Maybe while you're at it, since I'm legalistic and you don't like the 24 hour day, change the order that things happened in your eons of time.
Stop there? Why are jumping to Leviticus and the Law and the gospel? Absolutely no comparison about what we're addressing.
Legalistic? Funny you charge me with that because you don't agree. Everyone one this forum would charge you as a legalist with your position on baptism. Sad.