[quote="FrDavid96, post:12, topic:106344"]
No. It does not "trump" them---they are all in agreement with each other.
Check the link to Dies Domini. The sentence I quoted has a footnote which refers to the general norms for the calendar, so clearly the Church sees Dies Domini and the calendar norms to be in agreement rather than in conflict. The same goes for the Code of Canon Law. They all agree.
Gosh, I'm going to put my words in bold to break up the following paragraph:
:shrug: Perhaps I'm just dense, but I can't see how the statements "The liturgical day runs from midnight to midnight, but the observance of Sunday and solemnities begins with the evening of the preceding day," and "From a liturgical point of view, in fact, holy days begin with First Vespers" are reconcilable, unless one is speaking in a figurative sense that the observation of holy days begins at first vespers on the previous day, which is what the Norms seem to indicate... and if this is the case, then it is, in fact, incorrect to boldly state that the liturgical day begins at sundown, as this is in direct contradiction to the General Norms for the Liturgical Year...