Unsolved Mystery from 1780

On May 19, 1780 a phenom known as the Dark Day fell over the New England states. One account of the event reads "A thunderstorm from the southwest was accompanied by dark clouds and vapours so dense that it became necessary to light candles at midday. Farmers came in from the fields, birds returned to their roosts, and cows to their barns. Many people became so fearful that they abandoned their normal daily activities, and gathered in Churches to find "comfort" in religious services.Of course it wasn't long before the "doomsday prophets" began to exploit the incident with a "sensational" emphasis, to gain a following, attract audiences, or sell books. It was, they claimed, a fulfilment of the Bible prophecy in Rev 6:12 -- "The sun became as black as sackcloth of hair, and the moon became as blood."