This film brings us back to the First Class cast and finally introduces the core X-Men team that returns again in Dark Phoenix: Cyclops, Jean Grey, Storm, Nightcrawler, Beast, Quicksilver, and Mystique. While most of these characters have appeared in previous movies, this is chronologically the first time they show up in the timeline, with most of them portrayed as teenagers rather than as the seasoned adult heroes we meet in 2000's X-Men.
Apocalypse, like most of the other X-Men films, jumps around in time a bit, but the main narrative and conflict take place in 1983, where the X-Men have to work together to defeat Apocalypse and his Four Horsemen: Magneto, Storm, Archangel, and Psylocke.
It's important to remember that since Apocalypse takes place in the post-Days of Future Past timeline, nothing in this film got reset by Wolverine's trip to the past. So when Jean Grey frees Wolverine from William Stryker's facility, that's the new-timeline Wolverine, confirming that no matter what happened in 1973, Logan had a really lousy following decade.