If it's not at midnight it doesn't really count as the sunday obligation.
Which is plainly true to anyone deliberately following traditional Catholic teaching (although more precisely, I'd write "delayed until at least midnight"- , instead of "at midnight[/b]").
Nearly 41 hours later, I began to read this topic, and reïnforced 'tdrev123's statement:
There's no credible room for honest dispute [....]
Wow! Did the Holy Ghost give me a brief glimpse of future replies, or what!?
Most importantly, I cited Canon 32, and quoted very briefly from it:
[...] according to on-line translations of Canon 32 in the 1917 Code of Canon Law- , that for purposes of obligations, decrees, vows, &c., the ecclesiastical ["]day consists of 24 consecutive hours, to be counted from midnight to midnight" local time (as determined by whatever practical methods are available). So [the ecclesiastical "day" begins with] neither local sunset, nor local sunrise.
If you're limited to mediæval technology, get out your quadrant or sextant, then set your water-clock.
But I see that a dispute was indeed posted 11 hours later:
Actually Sunday starts with the Vespers on Saturday.
"Actually"!?  How so?  But lest readers fail to grasp a key consequence:
The mass after first Vespers fulfills the obligation.
Note bene: No sources whatsoever were cited.
Now, after years of membership in CathInfo, I know well that 'poche' has earned, um, a very special level of respect here. So when he wants to counter an assertion for which a source and quote was provided nearly 1/2 day earlier, he has no need whatsoever to cite and quote a source that supports his own contrary claim. It would be mean-spirited to insist that he provide evidence, because doing so would cut into the time he needs to sustain his rate of 6.45 postings per day (data limited to CathInfo). All 'poche' needs to do here is just state his claim, and it simply must be so!  He's just that special!
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Note #: I doubt that 'tdrev123' would disagree with my rewording, but if I'm wrong about that point, I suppose it'll be brought to my attention.
This story of St Notburga should illustrate how Saturday afternoon was considered the beginning of Sunday;
This little kitchen maid is very famous in her own country, high in the Alps mountains. She was the daughter of a peasant and went to work for a Count when she was eighteen. All the food she could save after each meal she gave to the many poor people who came to the side door of the castle. She even gave them much of what she was supposed to have for her own meals. The Countess was a mean woman, however, and she gave orders that Notburga was to give the left over food to the pigs, as had been done before the holy maid came.
For a while, the Saint obeyed, although she still gave the poor part of her own food. Then, she felt so sorry for those hungry people that she began again to give them food from the table. The Countess caught her and fired her at once. Next Notburga went to work for a farmer, and here, too, she was not afraid to do what she thought was right.
One Saturday afternoon, she stopped work when the Church bells rang, because Saturday evening was considered part of Sunday and no more work was done. Her employer, however, told her to keep working. Notburga answered that no good Christian kept working unless bad weather seemed about to spoil the crops. “The weather might change,” said the farmer. “We shall see about that,” answered the Saint. Then she threw her sickle up in the air, and there it stayed in the sky, looking like the harvest moon, the sign of good weather to come!
Meantime, the selfish Countless died, and the Count was having so many troubles that people said it was all a punishment for the Countless’ meanness to the poor and to St. Notburga. So when the Count married again, he made our Saint the housekeeper of the castle, and there she spent the rest of her holy life. Just before she died, she begged the Count not to forget to take care of the poor people she loved so much.
Whoever is charitable, will receive charity. Let us be charitable then, to those who are in need, with a little offering, or a helping hand.
http://thesaintsstories.blogspot.com/2008/07/st-notburga.html