I've always found the expression w dzień i w nocy a little paradoxical and a good example of the inpredictability of grammar rules. The 'paradox' is that w dzień uses w+Accusative while w nocy w+Locative, that is two different grammatical structures are used for completely equivalent meanings. I was wondering if there is any rationalization of this different treatment of `day' and `night'. Would there be anything logically or grammatically wrong with w dzień i w noc ? Thanks.