Blue Monday is called “Blue Monday” because it blends the old idea of “blue” meaning sadness with a modern marketing label for the “most depressing day of the year” in January.

Modern meaning

  • In today’s pop culture, Blue Monday is usually the third Monday of January and is promoted as the “most depressing day of the year.”
  • The term in this sense was coined in 2005 by psychologist Cliff Arnall for the UK travel company Sky Travel as part of a PR campaign to sell winter holidays.

The “formula” idea

  • Arnall said he used a kind of “formula” mixing factors like bad weather, debt after Christmas, time since the holidays, failed resolutions, and low motivation to pick this Monday.
  • Scientists and mental health organizations widely criticize this as pseudoscience, stressing there is no credible evidence that one specific day is the most depressing of the year.

Why the word “blue”?

  • In English, “blue” has long been linked to feeling down or melancholic, so calling it “Blue Monday” instantly suggests a low mood day.
  • The phrase “Blue Monday” itself existed in the 1800s, describing workers’ hangovers after heavy weekend drinking and later even a nickname for washday, again tied to the color blue and dreariness.

How it became a trend

  • Since the mid-2000s, brands and media have reused “Blue Monday” every January for attention-grabbing headlines, sales campaigns, or wellness tips, which helped the term spread on social media and forums.
  • Mental health charities now often “flip” Blue Monday campaigns to say that depression is real every day of the year, while the Blue Monday concept itself is just a catchy myth.

Quick forum-style takeaway

Blue Monday is called “Blue Monday” because marketers took the old “feeling blue” idea and turned one January Monday into a branded “saddest day” — catchy name, weak science, big PR.

TL;DR: It’s called Blue Monday because “blue” means sad, and a 2005 holiday PR campaign packaged one January Monday as the “most depressing day of the year,” even though there is no solid science behind it.

Information gathered from public forums or data available on the internet and portrayed here.