Then it'd be called "weekends", not "weekend".

We don’t call it “nights” even though one is split over two days (before midnight and after).

Just call it "evening" if it's before midnight. That way you get four nicely subdivided periods.

00-06 - night

06-12 - morning

12-18 - afternoon

18-24 - evening

Would need to refactor the name of "midnight" tho to minimize confusion. But if we use it as a starting point to count hours in a day from, it doesn't make sense to simultaneously designate it as a middle of anything.

(BTW, such subdivision is actually common in many places of the world.)

I feel we've just rediscovered why appeals to grammar[0] don't actually solve much of anything. (Not saying you're appealing to grammar, just that grammar is generally not that useful for discerning... anything really.)

Anyway, to be a bit more substantive: What really baked my noodle when I was younger is the fact that the seasons and the night/day cycle are much more disconnected than it appears when you live on Earth. Of course, it makes sense when you understand the tilt/rotation thing, but still... it really weirds me out sometimes.

[0] English in this case, but any language, really.