Kiri Chuunin Exam
Konoha Chuunin Exam
In this series, my main OC Konran takes the Academy graduation exam two years early (because Naruto has somehow canonically failed the graduation exam three times but is still in the same class as his agemates?) and somehow barely passes. She, along with two other OCs–Ringo Nohara and Zakuro Yuuhi–become a genin team under the jounin Riichi who is a minor canon character that I have co-opted as my own and tweaked slightly (or, rather, conflated with a different unnamed minor canon character) to give a cool backstory.
They end up taking the first Chuunin Exam which, because it’s two years earlier than canon, is not in Konoha but in Mist (I’m unsure about how much of a disaster Mist infrastructure was before Mei took over, but I imagine it’d be a HUGE faux pas if any of the big five shinobi villages passed up their year to host the exam. The smaller villages can get away with doing so, which is probably how Akatsuki stayed under the radar as leaders of Rain for so long, or rather it’s not as much of a surprise if they pass it up, but one of the big five? That’d just be embarrassing).
The Konoha Chuunin Exam is just a really good marker of time–since it’s not as if their team has changed Orochimaru and Sand’s plans, so the invasion is still on–and then ambiguous Shippuden point in time just to round it out.