If one attends a wedding Mass in the early afternoon on Saturday has the Sunday obligation been met?
First, let’s look at the Sunday obligation requirement from the 1983 Code of Canon Law:
§1 The obligation of assisting at Mass is satisfied wherever Mass is celebrated in a Catholic rite either on a holy day itself or on the evening of the previous day (canon 1248).
Two things are clear from this directive, one is unclear. First, what is clear:
*]The Sunday obligation is satisfied wherever Mass is celebrated in a Catholic rite: This means that the Mass itself does not have to be specifically a Saturday vigil Mass; it can be a nuptial Mass, a funeral Mass, an ordination Mass, an indult Tridentine Mass, an Eastern Catholic divine liturgy, etc. So long as it is a eucharistic liturgy celebrated licitly according to a Catholic rite, it meets the Sunday obligation.
*]Because the obligation is satisfied by any Catholic eucharistic liturgy, the readings of the Mass do not matter. The readings only matter in that they must be appropriate to the liturgy being celebrated; they do not determine whether or not a person can satisfy his Sunday obligation at that Mass.
In and of itself, a nuptial Mass may satisfy the Sunday obligation because it is an authentic eucharistic liturgy celebrated according to a Catholic rite. The only thing that remains unclear is the timing of the Mass:
*]Can a nuptial Mass held in the early afternoon on Saturday fulfill the Sunday obligation?
To date, Rome has not been specific about the time at which a Saturday Mass must be celebrated in order for it to fulfill a person’s Sunday obligation. This is an area over which canonists disagree, and over which we may hope that Rome will become more specific.
Here are two representative opinions from canonists:
The obligation to participate in the Mass may be satisfied at any time during the twenty-four hours of the feast day itself, on the evening before it. “Evening” should be understood as anytime from 4:00 PM onward. The legislator uses the word “evening” (vesper), not “afternoon” (post meridiem); in keeping with the proper meaning of the word … an afternoon Mass before 4:00 is not an evening Mass and does not satisfy the obligation (New Commentary on the Code of Canon Law, Canon Law Society of America, 2000).
What is “the evening of the previous day”? Despite the view of some commentators that this should be interpreted as beginning only at 1400 hours (2 PM) on that day, it is the firm view of this commentary that the evening of the previous day begins at midday (12 noon) on that day itself. In some dioceses there is a local regulation to the effect that the so-called vigil or anticipated Mass may not be celebrated before, say 5 or 6 PM… Those regulations do not in any way concern the time prescribed for fulfilling the obligation to assist at Mass: thus e.g. if in such a diocese a person were to attend a nuptial Mass in the early afternoon on Saturday, that person would have fulfilled the obligation … of this canon  (The Canon Law: Letter & Spirit, Canon Law Society of Great Britain and Ireland, 1995).
Until Rome makes a definitive ruling on the issue, the only definitive timing we have for fulfilling the Sunday or holy day obligation on the previous day is afternoon. You’re free to pick your “expert opinion” as to time in the afternoon, but the only clear restriction is that a Saturday morning Mass would not fulfill the obligation.