Being in the recruiting business, I learned early on that this causes a huge amount of confusion. Further complicating matters is the insistence that "next" needs to be used. Completely unnecessary. For instance, today is Tuesday. So I might say, "my daughter is graduating on Saturday." There is no need to say "this" Saturday, since it is implicit. Conversely, If I said, "my daughter graduated on Saturday." it is implicit that I am talking about the past Saturday which is obvious as the sentence is in the past tense.

Simpler is always easier and less fraught with confusion, so if your daughter is graduating on Saturday, there it is. I often ask people, "what is the difference between Saturday and this coming saturday?" The answer of course is there is no difference. So why bother with superfluous words?

Of course if I say, "next Saturday" obviously that means the Saturday after the upcoming Saturday. So the question to the confused person might be, "What is the difference between Saturday and next Saturday?" QED