As you might expect, tonight's flashback episode of Superman & Lois, titled "A Brief Reminiscence In-Between Cataclysmic Events," gave Superman fans a chance to look back at some of the key events that have shaped the life of this universe's Man of Steel. It also dropped some hints about the overall timeline of the Arrowverse in the post-Crisis on Infinite Earths continuity, including a few specific dates that give fans a better sense of when certain events were happening, outside of the very general "whiteboard timeline" that Cisco put together last season on The Flash. So let's dig in a little bit, shall we?
First thing's first, even if it came second in the timeline of the episode: During a brief flashback featuring Morgan Edge/Tal Rho, we discover that he established his desert Fortress and began training for world domination in 1987. That's ironic, considering that this is the post-Crisis timeline and in the comics, the Superman title from John Byrne, which followed his post-Crisis on Infinite Earths adventures and was published immediately following Byrne's The Man of Steel miniseries, launched with a first-issue cover date of January 1987. This suggests that Rho likely landed on Earth somewhere around 1970, which is interesting. It also means that he was honing his powers and looking for The Eradicator for nearly 30 years before Superman's arrival in Metropolis.
That's because after Clark learns of his powers from Jor-El, and returns to Smallville, he tries to seek out Lana. When he does see her, she's standing outside a movie theater, waiting for a date with Kyle. On the marquee: A Harry Potter double feature, and Friday Night Lights.
Not only is Friday Night Lights a kind of meta reference, since the producers of Superman & Lois have repeatedly invoked the movie's TV adaptation as a key influence on their approach to the Man of Steel, but it definitively pegs Clark's return to Smallville -- and his move to Metropolis -- as being in 2004, since the film was released in October of that year.
In June of that year, the third Harry Potter movie (Harry Potter and the Prisoner of Azkaban) was released, so the double-feature is likely the second and third movies in the franchise. Although since Azkaban would not have been in theaters in October, having ended its run in September, it's possible that it could be any combination of the first three movies, as the double feature in Smallville would likely have been a special arrangement by the theater.
In any event, this suggests that Superman made his debut in Metropolis in late 2004, meaning that by the time the Crisis happened, he had been in action for 15 years. Since Jefferson Pierce was active as Black Lightning until around 2011, according to the loose timeline laid out in that series, it seems likely that the pair must have teamed up (or at least been aware of one another) at some point in their early careers. Batman was also active during that time, and Supergirl was on-planet, but not yet a costumed hero. It would be 2011 before the new age of heroes really began with the arrival of Oliver Queen's Hood/Arrow/Green Arrow.
Superman & Lois airs on Tuesdays at 9 p.m. ET/PT on The CW, following episodes of The Flash.