(you are right it is slightly tedious those details, but well done) Overall it seems striking to me that the seven day week itself is one of the enduring and fundamental features of the ancient world that has so thoroughly formed the fabric of modern life in the West and elsewhere.

Oh yeah true. Then... palm sunday is the exception?

No, it's the first day of the holy week

Liturgically, the day begins at sundown and both the Holy Week and Paschal services are moved to the beginning of the Liturgical day “in anticipation”. So the Lamentation service of Holy Saturday will have been said on the calendar-Friday and the first services of Pascha, the Rush Procession and Orthros (Matins), will start on calendar-Saturday. So, Pascha begins on Saturday, but also on Sunday depending on your reference point.

There are places like Mt. Athos, West Bank monasteries they actually keep time like that https://en.m.wikipedia.org/wiki/Byzantine_time

So sundown is 00:00 and so on.