Bear in mind that there were no telephones; there was no radio or television; there was no telegraph. People often lived far away from their nearest neighbor. They knew little of what, at a given moment, was happening outside the patch of land where they resided.
The one thing a person could always count on -- that the sun would come up in the morning and stay up until evening -- suddenly could not be counted on at (http://www.cnn.com/2013/05/19/opinion/greene-day-of-darkness)
Religious interpretations
Since communications technology of the day was primitive, most people found the darkness to be baffling and inexplicable. Many applied religious interpretations to the event. . . .
Today, some Christians, especially those among Seventh-day Adventists citing extracts of Biblically sequential events, "... the sun will be darkened, the moon will not give its light, the stars will fall from the sky..." (Matthew 24:29 (WEB) are signs preceding the return of Christ) and interpretations of the event as cited by Ellen G. White, believe that the Dark Day was a fulfillment of Biblical and end-times prophecy.[9][10] Also see Revelation 6:12–13 "... and there was a great earthquake. The sun became black as sackcloth made of hair, and the whole moon became as blood. The stars of the sky fell to the earth, like a fig tree dropping its unripe figs when it is shaken by a great wind." One prominent Seventh-Day Adventist, Arthur Maxwell, even mentions this event in his The Bible Story series (Vol. 10). Some Progressive Adventist scholars do not interpret this as a sign of Jesus' soon return.[11] Traditional Historic and Conservative Adventists, who hold Ellen White's writings in higher regard, still consider this date as one of the fulfillments of biblical prophecy.[12]
9. Bible Universe. Retrieved from http://www.bibleuniverse.com/prophecy/sun_darkness.asp.
10. The Dark Day. Retrieved from http://www.bibleprophecytruth.com/JesusChrist/thedarkday.asp.
11. Graeme Bradford, "Ellen White and the end times", chapter 17 in his More Than a Prophet. Berrien Springs, Michigan: Biblical Perspectives, 2006, p139
12. White, Ellen G. Maranatha. Napa, Idaho: Pacific Press Publishing Association, p. 150
http://www.signs-of-end-times.com/celestial-signs-sun-stars-moon.html
http://www.web-books.com/Classics/ON/B0/B897/09MB897.html
In about 1886 a former slave named Harriet Powers crafted a quilt with one of its panels dedicated to New England’s Dark Day, ... (http://web.massar.oorg/may-19-1780-new-englands-dark-day)
Cause (A Theory): The likely cause of the Dark Day was smoke from massive forest fires. When a fire does not kill a tree and the tree later grows, scar marks are left in the growth rings. This makes it possible to approximate the date of a past fire. Researchers examining the scar damage in Ontario, Canada, attribute the Dark Day to a large fire in the area that is today occupied by Algonquin Provincial Park. (Ref. 13, 14 - http://en.wikipedia.org/wiki/New_England%27s_Dark_Day)
http://www.bbc.com/news/magazine-18097177
http://www.islandnet.com/~see/weather/almanac/arc2004/alm04may.htm
A supernatural phenomenon!?! Or a major forest fire happening hundreds of miles away?