As previously stated and easily checked - video games (especially RPGs) have had D/N cycles some 20 years ago
Make it even 30.
Ultima VII, a game that even Swen Vincke knows very well and claimed to love and admire in the past, had it in 1992. And in a fairly complex form too, one that I wouldn't even ask from Larian, with a lot of reactivity tied to it.
Looking at their own games, it's often surprising to me that Larian/Swen are this huge fans of Ultima VII.
Ultima VII is kind of a platonic ideal, and even a stand-out in the Ultima series. It's at least at much a world simulator as it is an RPG. Had Origin continued, and gone down this route in the same way, we'd be dealing with even more complex stuff by now than NPC schedules, day/night/cycles or every item being pick-upable. Like, maybe even a fauna economy, e.g. animals in the world having a life-cycle, being born, maturing, mating, dying, fighting each other and occupying terrorities etc. In Ultima VII, the game world was as much a star as was the protagonist and the plot he unravels.
The DOS games, and neither BG3, aren't anywhere near. They share some similatiries, in that lots of objects are interactive, and that it's all being viewed form an isometric view. But if that upsets Swen, that's about it. Else they're pretty staged and static, and the DOS games with their "level gating" forcing players to tackle any one map in a partiulcar way even more so than BG3. In all of these games, the player is the totally centre stage of anything, and everything is carefully scripted / build for his -- without his involvement and questing, nothing much every changes and moves.
Sure, you could be even further removed from anything Ultima7, but Larian have never been particularly close.
The original BGs, for that matter, have also been comparably static in comparison to anything like it, to be fair. That said, yes, the day/night cycle as well as weather changes provided lots of additional atmosphere, in particular in BG1, which for a bulk of a game had the player's party adventuring the wilds. On the occasion, it was used for further, such as the vampire ambushes in BG2, which naturally would only happen at night.
