Why "Anticipated"?

[Vico]

In any case, it seems like it’s disciplinary. If there are any theological overtones, I’d like to hear them.

The theology of time, pertaining to Sunday, is that it is the eighth day, the day of the Resurrection. The start of a day varied. In the ancient Church, the day began at different times:

Athenians: sunset to sunset
Romans: midnight to midnight
Babylonians: sunrise to sunrise
Umbrians: noon to noon

The time for celebration of the Eucharist in the ancient Church was different than today. They were know for gathering together before sunrise and after sunset, they were night-owls.