Posted by  - Quartz Obsession
In modern times, we celebrate the dawn of a new year by saying a dramatic “good riddance” to the old one. Please see: “2018 Was the Worst Year ever!” (Twitter said the same thing about 2017… and 2016… and 2015… and so on.)
But what really was the worst year to live through? 
The year 536 is a good contender. That’s when a mysterious haze settled over most of the northern hemisphere and threw much of the world into an 18-month period of constant darkness. Around the world, temperatures plummeted and crops died. In China, snow fell in the summer. In Ireland, farmers were unable to make bread for the three consecutive years. Disease and pestilence boomed; bubonic plague wiped out half the population of Constantinople. 
536 kicked off the coldest decade in more than 2000 years and was the doorway to the dark ages. Harvard medieval historian Michael McCormick told Science magazine that it “was the beginning of one of the worst periods to be alive.” Time to take the toll.
The origin of the Late Antique Little Ice Age
For centuries, the cause of 536’s chilly, dark fog was something of a mystery. By the late 20th century, scientists studying tree rings concluded that the culprit was likely a massive volcanic eruption. Just a few years ago, researchers studying ice cores from Greenland and Antarctica found a 1500-year-old layer of sulfur and bismuth that confirmed this volcanic hypothesis.
Since then, researchers have been trying to determine where, exactly, the eruption occurred. Most assumed it happened somewhere in North or South America. But according to Ann Gibbons at Science magazine, researchers at the Climate Change Institute of the University of Maine recently pinpointed the volcano’s location in Iceland. 
Details about the awfulness of 536 tend to concentrate on Europe, but a similar event shook the southern hemisphere in 540, when the Ilopango supervolcano in El Salvador erupted. The explosion was so intense that it possibly caused the Mesoamerican city of Teotihuacan—then the world’s sixth largest city with 200,000 people—to suffer a major decline, precipitating its collapse. The eruption also contributed mightily to a South American dark age called the “Maya Hiatus,” a period which eventually led to the downfall of Mayan civilization.
A third volcanic eruption in 547 sealed the fate of the 540s, which had a global average temperature over five degrees Fahrenheit cooler than modern temperatures.
“And it came about during this year that a most dread portent took place. For the sun gave forth its light without brightness, like the moon, during this whole year, and it seemed exceedingly like the sun in eclipse, for the beams it shed were not clear.”  —History of the Warsby the Byzantine historian Procopius