But in theory, ID and Evolution could easily coexist.
No, they cannot!
One is knowledge the other is propaganda from a particular christian sect.
Secondly, one could believe that a world was created by an intelligent being, and that creatures evolved since then.
Sure, you can believe the big bang was done by an intelligent being, it's a theory. I don't think it's a good one but we don't exactly know the right answer yet, so in the meantime someone can call it god. There is no reason to believe there is a personal god though and there is enough evidence that we can say the world isn't created in a week and surely not some 1000 years ago.
Also, a day has not always been standardized, assumedly the "7 Days", is not made up of 24 hour days. The way it is written, it likely refers to a period of time only.
Or it's probably just not true and written by plebs. Read the first page of the bible and do you honestly think it's an acceptable explanation for the creation of the entire universe? I think it would be pretty insultive to god's intelligence if there was one.