I can understand that “vespere” can have some flexibility.
If I were in Norway or Alaska today (late December) and a Mass started after sunset, I would be perfectly content to look at the sun (or lack thereof), while ignoring the clock, and have no problem, no hesitation, that a Mass after sunset would fulfill the obligation for tomorrow (let’s say, for discussion sake, that today is Saturday).
I can also understand a pastoral response from a bishop in one of those places who wishes to avoid confusion in the Mass schedules, and who permits the time of sunset in winter to be applied throughout the year. I don’t know if this happens in reality, I’m simply saying that I respect the bishop’s authority to interpret for his diocese.
I can understand some flexibility and the value of avoiding anxiety.
What I cannot understand is "how can one say that vespere begins at meridiem?"
I have not seen any actual answers to that question.
I’ve seen answers based on the word “evening” in English. I’ve seen answers that quote non-English commentaries and/or translations that use words which may mean anytime after noon in those languages. I remain unconvinced by these positions, given the reasons I’ve repeated here often enough.
Thus far, I have not seen any actual explanation, nor any actual reasons why the Latin word “vespere” can mean “the evening of the previous day begins at midday (12 noon).”
Starting with Pope Pius XII in
Christus Dominus (1953)
papalencyclicals.net/Pius12/P12CHDOM.HTM we have a precedent that an evening Mass cannot begin before 4 PM (see Rule VI) Even though Pope Pius was addressing a Mass on the same calendar day, (not an evening-before), there’s no ambiguity with regard to 4 o’clock. Given a solid precedent like this, quite frankly, I feel that someone who advocates that “evening begins at midday” should provide some actual reason, some convincing premises, for arriving at that conclusion. Pius XII himself even tells us that 4 o’clock is early evening (if evening did begin at noon, then 4 would be the opposite, late evening).
The mere statement “the evening of the previous day begins at midday” is not enough to convince me.
The only explanation that I have seen was referenced here on CAF many years back. I cannot find it, though I’ve looked. It referred a writing by someone in the U.K. who based the reason on a Southern US slang use of evening. Was that the GB&I Commentary? At times, I thought it was, but maybe it is not. I don’t have the printed text. It may have been a different source. What I do remember is that it was a lengthy piece, as opposed to just a paragraph or two.
So, again, I will ask "how does vespere begin at meridiem?"