Time tracking would be useful for a lot of the existing quests: the grove ritual, the goblin attack, the burning building, the Zhentarim leaving their hideout, the poisoned gnome, the toxic fumes in the collapsed cave, etc.
What you are describing here are timed events ...
They can easily be implemented in curent system by simply adding number of Long Rests (aka Days) into quest log ... and implementing apropriate effects, once their timer reach 0.
Day/Night cicle is something (not-so-entirely, but still) different ...
People required option to move around the map "in the night" ... there was even some suggestion around here so we can simply skip rest of the day, so we can move around in the night ...
Purely for aestetic purposes, since people were talking how odd it seems that "Drow attack the Grove during daylight" ...
Therefore they obviously wanted to let the event exactly as it is, just move it half day later.
Yes, there was even more complex suggestions, where people demanded ingame clock that would represent REAL time flow ...
But if that would include day/night guard/shop shifts ... different creatures you could meet ... spells actualy lasting "one day" if they are suppose to ... and timed events mentioned earlier ...
I agree it would be freaking awesome ... but it would also require lots of additional time and resources. :-/
I aree tho, that it would be most polite from Larian to ask their new Comunity Manager (since we finaly have one) to tell us if they were even thinking about this, and if so what (and why) was their decision ... this one-sided comunication is indeed frustrating as fuck.
It's not (only) nostalgia
I presume it depends on poster.

For some (and i could name, but moderators wouldnt like it), it most definietly is.

And while implementing the passage of time, they could add a fatigue system which would be a neat way of encouraging long rests (which would then offer all these cool cinematics they spent so much time working on).
Maybe im naive ... i mean, in this aswell as other topics ...
But i still believe that some kind of fatigue is planned, and they just want to have as much data about people resting as possible to not make it too loose, or too restrictive ... otherwise, what for would be those potions against exhaustion ... since Berserker Barbarian dont get any?

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Both claims wrong, incidentally.
Lets trade quality for quality in this argue:
Nope.