Dark day
Members of the U.S. national newsmedia oligopoly often use the phrase
"dark day" to mean "bad day".
An actual dark day is a highly overcast day,
such that the eye-burning, skin-burning, vulgar bright light of the uncovered sun
has been largely blocked, resulting in non-vulgar, relatively beautiful lighting.
Thus, to use the word "dark" to mean "bad" is to say
"vulgarity is good; beauty is bad".