Three Days of Darkness

The Three Days of Darkness is an eschatological concept regarding future events, held by some Catholics to be true. The prophecy foretells three days and nights of "an intense darkness" over the whole earth, against which the only light will come from blessed beeswax candles, and during which "all the enemies of the Church ... will perish."

The prophecy parallels the Ten Plagues against Egypt in the Book of Exodus (Ex. 10:21–29). The Apocalypse of John also mentions a plague of unnatural darkness as an effect of the fifth vial (Rev. 16:10). Rev 16:10  And the fifth angel poured out his vial upon the seat of the beast; and his kingdom was full of darkness; and they gnawed their tongues for pain,  However, the specifics of the "Three Days of Darkness" prophecy are derived from private revelation.

There are some attempts to claim that the sixth seal will provide some plague of unnatural darkness (Rev. 6:12) "Rev 6:12  And I beheld when he had opened the sixth seal, and, lo, there was a great earthquake; and the sun became black as sackcloth of hair, and the moon became as blood;"

Advocates
Blessed Anna Maria Taigi (1769–1837) is the most known seer associated with the Three Days of Darkness prophecy and reportedly described the event as follows: "There shall come over the whole earth an intense darkness lasting three days and three nights. Nothing can be seen, and the air will be laden with pestilence which will claim mainly, but not only, the enemies of religion. It will be impossible to use any man-made lighting during this darkness, except blessed candles. He, who out of curiosity, opens his window to look out, or leaves his home, will fall dead on the spot. During these three days, people should remain in their homes, pray the Rosary and beg God for mercy. All the enemies of the Church, whether known or unknown, will perish over the whole earth during that universal darkness, with the exception of a few whom God will soon convert. The air shall be infected by demons who will appear under all sorts of hideous forms."

Marie-Julie Jahenny (1850–1941), known as the "Breton Stigmatist," expanded upon the story of the Three Days of Darkness. According to Jahenny, it would occur on a Thursday, Friday and Saturday; all of Hell would be let loose to strike at those outside their homes and those without a lit blessed candle of pure wax. These candles would miraculously stay aflame the entire period, but not light at all in the houses of the godless.

Controversy
Some sedevacantists hope that a true Pope will be miraculously designated by an apparition of Saint Peter and Saint Paul; this tangential belief assumes that the pontiffs in those times of the Church will be, in fact "antipopes". There is also controversy over whether the twentieth-century saint and stigmatist Padre Pio endorsed and taught on the future Three Days of Darkness, as the authenticity of the alleged words of Saint Pio are disputed. The authenticity of Anna Maria Taigi's purported description of the events in the prophecy has itself attracted doubt.