The firat is good. The second is not. Should is a recommendation and not really an unreal situation.

Hey! I think the first sentence sounds good and the second one maybe a bit odd.

The second sentence, as it's written, would not be correct. However, with some modifying, it could be. For instance: "If there should be 25 hours in a day, then there also should be an extra hour for sleep." While this may not be the most natural sounding sentence, it's grammatically and logically correct. I hope this helps =)

The second one is wrong :)

If there should be 25 hours in a day, ... this is definitely wrong!