This is not a straightforward answer and timeline, because the book, "A View from Saturday" skips around all over the place via multiple flashbacks to the students that are a part of the "The Souls." This is the name that the students chose to call their little group and team name in the academic knowledge bowl tournament.
The reader knows that the book starts in May. That makes sense. Usually a school academic challenge will be during the school year and at the end of the year. That way the team has the most time to practice, and the teacher has the most time to build their knowledge base.
The first two flashbacks are centered around Nadia and Noah. Both of their flashbacks take place during the previous summer. So, sometime between June 1 and September 1. Both flashbacks take place in Florida as well.
Julian's flashback begins on the first day of school and jumps around, in sequence, to various events that happened to him that school year until the competition in May.
Ethan's timeline is a goofy one. Technically he also starts out in Florida, but the reader learns about it from Nadia's flashback. Another starting point for him could be the bus. That's where Julian's story overlaps, and it's where Ethan's main story begins. There's a lot of intertwining happening throughout all four characters, and it all begins happening the summer before 6th grade year. The intertwining and depth of their friendships is what continues during the 6th grade year.
Mrs. Olinski's timeline of events is focused on the actual school year. But her story starts 10 years earlier when she and her husband are in a car accident. He is killed and she is left paralyzed. She doesn't teach for the next 10 years. This is her first year back.
I wish I could tell you exactly when the last chapter of the book takes place, but it's ambiguous. It's likely sometime after the school championship, because the reader knows that The Souls go on/went on to win the state championship.