Translation:September is not a day, but a month.
I've also heard that utan is often used to signify a strong correlation between two things, where [It IS this, NOT that] - rather than a [but I was doing such-and-such]... Is this right?
The point is, that in English "but, rather" has the same meaning as "utan" in this context. If the point of this question, is to translate that meaning into English, then he is absolutely correct. Rather does NOT mean that one is better than the other, is this situation, it has the exact same meaning as "but" a month (the only real difference, it that it sounds MUCH more natural to use "rather").
If he was using googletranslate, or something, it would never give him that translation, but I believe that we're better than that, no?
Is it fair to say that when used as a conjunction, 'utan' could mean 'but instead?' Like if I wanted to use these approximate words to say this in English, I might say 'September is not a day, but instead is a month.' Of course, really in English, I'd just say 'September isn't a day; it's a month.' But I'm trying to use the given phrasing.