On 20 December 2016, Facebook users began sharing a link to an io9 article reporting that "tonight" would be the "darkest night in 500 years":
Thanks to a lunar eclipse on the longest night of the year, tonight we'll be experiencing the longest, darkest night in a very long time. It's been nearly 500 years since the last solstice lunar eclipse ... Over at Sky and Telescope, you can get the real story on what the five possible stages of the eclipse are.
Some news outlets even picked up on the claim and reported it as current in December 2016. As it happens, the io9 article was accurate ... but that was the case back in 2010, not today:
The evening of 20 December 2016 won't be the "darkest night in 500 years," nor will it coincide with a lunar eclipse, as the next occurrence of the latter phenomenon won't take place until February 2017.