There are dangers in replacing the Teachings of the Church with fallible (even though sometimes approved) apparitions. One should first be grounded in the Catholic Faith.
I’ve seen time after time people who put more faith in Seers and Apparitions and ignore the basic teachings of the Church.
Even approved visions, locutions etc are not a substitute for the teachings of the Church. They do not have the guarentee of authenticity, even if the claim is that our Lord or Lady themselves stated what the seer says to be true. They are PRIVATE REVALATION, and not a part of the official teaching of the Church.
Weeding out what is and is not approved by the Church is often times hard to do. Let’s take for example an alleged apparition of our Lady in Egypt. It is proported by many Roman Catholics that it has the approval of this or that Bishop, Archbishop or the Pope.
Well that is and is not true. It does have approval from the Bishops and Pope of the Coptic Orthodox Church. The Coptics are a Non-Chalcedonian Church, that is they are not simply not in communion with the Holy See, but they also hold to the monophycite heresy which states Jesus has only one nature the Divine Nature, and only appeared to have a human form. As our Lord is not the author of confusion, and there are Coptic Catholics who do not accept the heresy, I don’t know why someone would mix apparently false apparitions at the Orthodox Cathedral with approved Catholic Apparitions.
There are a number of “Seers” in Central and South America, one in particular who is divorced and re-married, another who has been debunked (She presses rose petals with religious metals and claims that God Himself embosses the petals with the images) There are seers who contradict the teachings of the Church, but have followers who accept them as Gospel.
While the three days of darkness does seem to have credibility, and if taken as a pious belief and not a dogma of the faith is not harmful. Promoting it as Dogma, or in place of dogma is putting the cart before the horse. I’d rather sit down with a copy of the Bible, (Catholic Edition of course) A copy of Dom Orchard’s “Catholic Commentary on the Holy Scriptures” A copy each of the Catechism of the Council of Trent, and Fr. John Hardon’s Catechism, and learn what the Church regards as required of Catholics to believe and do, and once I’ve learned the Faith inside and out, then deal with such lesser important issues as three days of darkness which are not a part of the deposit of the Faith.