AN 8.42
Eight essential factors in the observation of the Buddhist Sabbath
with an explanation of why this practice is so fruitful.

Uposatha

Very interesting from the point of view of the comparative life-spans of some of the gods above the human realm. In this we have an anticipation by about 2500 years of Einstein's Theory of Relativity ... adding some things Einstein didn't think of.

Combine this with an understanding that the paṭicca samuppāda anticipates quantum physics and whole new worlds of possibilities open up ...

But not so long as we have the seven-day work week throwing off the natural rhythm of life as would be lived according to lunar and solar time.

In balance with the cosmos, one can see into the cosmos, find one's place, achieve balance;
off balance, the sight of man is continually seeking just to find balance.

We see the result of that in the focus on the buck.

Organize the calendar according to the convenience of the merchant in the seven-day work-week and the mind naturally concludes that the goal of the merchant (the buck) is the source of balance in the world.

Think of the ramifications in terms of health, status, power, satisfaction.

I suggest that the powers that be when the world grinds to a halt
(some time after the election: (Edit: That was the election of 2016, and the world is romping along, if madder than ever.))
from the utter boredom of this meaningless pursuit, that in stead of instigating a new war to liven things up, they change the calendar.

References:

AN 8.43 Eight essential factors in the observation of the Buddhist Sabbath with an explanation of why this practice is so fruitful.
AN 8.44 Valetta is told of the eight attributes of the Upasatha and remarks as to how much it would benefit others to so practice.