The Question and Answer section for Wonder is a great resource to ask questions, find answers, and discuss the novel.
Julian was looking at Auggie in a way that drew attention to him. Auggie knew Julian was saying that he (Auggie) looks like a freak. Auggie uses a Star Wars metaphor to prove his point.
From the text:
Every year in the spring, the fifth graders of Beecher Prep go away for three days and two nights to a place called the Broarwood Nature Reserve in Pennsylvania.
I see no evidence of the novel mentioning the day of the week.
Much of the tone of the book is delivered through Auggie. He is a wistful and funny individual. He likes to think of fantastic situations that would make his life better.
If I found a magic lamp and I would have one wish, I would wish that I had...