[Philly06Cup]

I'm having an argument with my sister over what day "Next Sunday" is.

So today is Saturday, April 21. Would "Next Sunday" refer to Sunday April 22, or Sunday April 29?

I contend that Next Sunday refers to Sunday April 29 -- if I wanted to refer to April 22, I would've said "This Sunday," or "Tomorrow." She retorts that a week is from Sunday through Saturday, therefore "This Sunday" would mean Sunday April 15, and "Next Sunday" should mean the Sunday of the next week, i.e. tomorrow, Sunday April 22.

But that makes me wonder: Pretend today is tomorrow, then what day would "Next Saturday" be? To most people, I think, it would probably be Saturday April 28; but my sister still contends that Next Saturday would mean Saturday May 5, and that April 28 would indeed be This Saturday.

So, to anybody who is still following -- who is right? And which do you say/use?