The idea is that those who did not give or receive gifts on Valentine's Day (February 14) or White Day (March 14) can get together and eat jajangmyeon, white Korean noodles with black bean sauce, to celebrate their singledom.
a Black Day a day when something very unpleasant or sad happens
Black Day Blue Night (1995)
A disgruntled wife of a cheating husband takes off on a road trip with her husband's "other woman". The two women pick up a hitchhiker who may, or may not, be a robber and murderer on the run from the cops. In the mean time, a policeman who is tracking the robber/ murderer is hot on the trail
Depeche Mode Black Day Lyrics
Celebrate the fact
That we've seen the back
Of another black day
Celebrate the fact
That we've seen the back
Of another black day
Black day
Black day
I want to take you in my arms
Forgetting all I couldn't do today
Black Day
Black Friday (shopping)
Black Friday is the day following Thanksgiving Day in the United States, traditionally the beginning of the Christmas shopping season. On this day, many retailers open very early, often at 4 a.m., or earlier, and offer promotional sales to kick off the shopping season, similar to Boxing Day sales in many commonwealth countries.