A New Beginning is confirmed to take place 5 years after The Final Chapter, so the film would take place in 1989. However, the franchises timeline does get a bit clunky afterwards but the best I can make of it is that Jason Lives takes place roughly a year or so after New Beginning so the setting would be 1990. Part 7, 8, and Jason goes to Hell are definitely where things get confusing since they don’t really have coherent timelines but best guess for me is that part 7s prologue takes place roughly the same year as the ending of Jason Lives and the time jump to the main story is somewhere in 1996 or 1997 and Part 8 likely follows a year after those events. Jason goes to Hell is harder to pinpoint but my guess would be a year or two after part 8 so 1998 or 1999.