MangaDex

The following is a timeline of events occurring in the original continuity of JoJo's Bizarre Adventure and related series such as Thus Spoke Kishibe Rohan.. Part 3 lasted 50 days. Part 4 lasted around 8 months give or take, since it ended during Josuke's summer break. Part 5 lasted no longer than a week at most. Maybe even a few days. Part 6 lasted a few months, especially remembering how long it took for Weather and Hermes to recover from their injuries. Part 7 lasted around three months.

There is some confusion in the series about whether Stardust Crusaders takes place between 1988 and 1989 like you said or between 1987 and 1988. In part 4 characters seem to flipflop between the two dates, but part 6 sticks with the 88-89 version. You can read about it here. As someone else said, Stone Ocean does start in 2011 but it runs into.. Jojo's Bizarre Adventure's continuity can be confusing for new fans. So, here's a guide on how to watch it according to story arcs in order.