This forum can be used to gather some information about the Catholic Church, Catholic practices, etc, but as I’ve found out, in all charity I do have to remember it’s still the Internet. There’s no way that I know whether a particular response was made by someone with actual knowledge about a specific topic. In other words, I could be reading the response of a canon lawyer or a priest. Or I could be reading the response of an anti-Catholic with an axe to grind, or a school child who ought to be doing his/her homework.
Most dioceses have websites, and there are usually “frequently asked questions” menus. Minimally, they post the chancery’s phone number. Alternately, a local parish is a good resource for questions. If you live in the United States, the USCCB has very good, official information on its website, including some very sophisticated links, as do the state conferences of Catholic bishops.
I do, however, “feel your pain.” Last Holy Saturday, I was working at my hospital, and since I had a quiet afternoon ahead, volunteered to take several stable patients to Mass in the hospital chapel at 2 PM. The daytime Mass of the Resurrection was used. I was under the impression that I had thus fulfilled my Sunday obligation, and slept in on Easter morning.
A few weeks after Easter a similar thread as this appeared on this forum. The general comment was that the “cutoff time” was 4 PM, with a few other opinions such as “after dark,” etc. That gave me some doubts, so I posted the above scenario, and had a few people tell me that no, I had not fulfilled my Sunday obligation and had better go to confession, especially if I had received the Eucharist since (I had.)
So I went to confession and confessed all of this, only to have the priest tell me that a) each diocese has different times on Saturday that fulfill the anticipated Mass obligation, b) I was acting in good faith since I did not know what time that was, c) I had performed a spiritual work of mercy by taking those patients to Mass, and d) how and where to get correct information on such matters. He concluded by telling me that I had not committed a mortal sin since I did not know that the 2 PM Mass didn’t fulfill the obligation, as committing a mortal sin requires sufficient knowledge as one condition. He then told me to figure out something else to confess!
I left the confessional feeling a little sheepish about having my peace of mind disturbed by the Internet Curia, however well-intentioned they were!:o