Documented history goes back a lot further than science. We have written chronicles of dates when people were surprised that the sky grew black and the sun didn't shine. Oh yeah, they knew weather, but some dark days couldn't be explained by storms. In October of 1762, the skies over Detroit turned black and a sulfurous rain fell that was black even when it hit the ground. There was no industrial pollution back then, so what was it? We don't know to this day. One day in 1857, the skies over Baghdad turned black for a short time, then red, with red sand falling over the town. In 1938, skies over Siberia turned black. No rain this time, but accounts from that day tell us that radio signals could not get in or out in the region.
Many historical accounts of daytime darkness can be explained now as solar eclipses or volcanic clouds. But those weren't the explanation for any of the eight mysterious dark days on this list. A couple can be explained by rare weather phenomena, but most have no definitive cause to this day. Read about eight incidents of daytime darkness at Mental Floss.