Earlier quoted context omitted.
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).
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.)