The “This Is Us” season four return marks the midpoint of mid-season debuts for broadcast TV in January, part of the NBC slate that’s been off the air since Thanksgiving. But the series, which itself is also balanced at its own midpoint with two and a half more seasons to go, has now revealed the full scope of its ambitions. (NBC has greenlighted the series through season six, which show creator Dan Fogelman has suggested will be the series finale.)

Unlike most so-called prestige TV series, which wear the grand scope of their narrative like a badge of honor, “This is Us” has spent three and a half seasons slowly unfolding. It’s a show that looks and feels familiar, a small-scale tale of a single family. But with the fourth season reaching out into the future after spending three seasons in the past, “This Is Us” is now covering a full century of time.

Unlike most so-called prestige TV series, which wear the grand scope of their narrative like a badge of honor, “This is Us” has spent three and a half seasons slowly unfolding.

When “This Is Us” premiered, it presented itself as a generational story with two points: The parents — Jack and Rebecca Pearson (Milo Ventimiglia and Mandy Moore) — in the 1980s and the children — Kevin, Kate and Randall Pearson (Justin Hartley, Chrissy Metz and Sterling K. Brown) — in the 2010s. For most of the first season, it stayed lodged between these two endpoints, building toward the death of Jack in the mid-1990s.

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But using the past in this way could only sustain the series for so long. By midway through season two, Jack’s death was no longer a mystery. Moreover, his death was not portrayed as the reason why these people are who they are, but merely a fork in their divergent life streams. Such reveals are truer to life, but not nearly as rewarding, and season three found itself with a ratings drop, going from an average of 11 million viewers a week in season two to barely 8 million in season three.

But those who lost interest were missing out. Season three began pushing further into the past, filling in time between Jack’s birth in 1944 to where the show introduced him in 1980. At the same time, it began adding in mysterious flash forwards, bringing the characters’ futures from the 2030s into the narrative. By doing so, the show added in a new layer of mysteries, with the period between present day and the 2030s left to be explored.

It’s the endpoint of the future that really shows the length and breadth of the series’ ambitions. Season four opened with what felt almost like a soft reboot, sidelining the entire regular cast to focus on three characters who would become important to the family’s future. Two of these characters intersected with the main stars within a few episodes. But the third threw the show even further into the future, to the year 2044. In short, the show has now created a story that covers a full century of American life.

That means the furthest “This Is Us’” timeline point now stretches nearly as far as HBO’s dystopian futurist series “Westworld” (set in the 2050s). But don’t expect Fogelman to introduce android hosts or flying cars. The show isn’t interested in what lies ahead for America as a society in the 2040s, any more than it was interested in the political landscapes of the decades it has already covered. (The Pearson parents seem like the typical Reagan voters of the 1980s, but despite the show crossing several election years between 1980 and 1997 — and a focus on Vietnam — politics magically never comes up.) For “This Is Us,” the essential truth is that a century of time can and will pass, and yet family, in whatever form it takes, is unchanging.

This generational story has been hiding in plain sight. We might coo a little over Moore’s 1970s dresses, or Kate’s 1990s flannels. But the truth is from the outside, it looks like “This Is Us” is just another broadcast family drama.

But for viewers, change is everywhere — social, technological, climate. Time seems to both expand and collapse as we are inundated with information. We fear as a society that the planet has reached a point of no return. Our political world is so untenable that war and mass murder are now regular byproducts. Against that backdrop, “This Is Us” reminds us that be it 1944 or 2044, relationships are still the center of what matters.