You needn’t be an expert in psychology to pinpoint January as one of the least enjoyable months of the year: the excitement of the holidays has concluded while related bills begin rolling in, the coming of a new year is for many people a reminder of passing time that prompts sad reflections about missed opportunities and accomplishments, no extended breaks from school or work are in the offing, and in many parts of the northern hemisphere the weather is unpleasant if not downright dangerous. It’s often cold and drab out, with summer a distant memory nearly half a year away. But is any date on the calendar in January statistically the most depressing day of the year?

Social media users have frequently posted about “Blue Monday,” a term assigned to any number of specific days in January (typically the third monday of the month). Rumors abound that a particular date (typically a Monday) has been deemed by scientists or researchers to be the most depressing of the entire year, with a number of factors influencing the calculation of this bummer of a date. Going by popular lore, you might believe we scarcely can control our level of contentment on that day given all the mathematical reasons for us to be well and truly miserable.

The concept of a “Blue Monday” took root in 2005. In that year, a press release detailed a purported formula that calculated factors including weather, debt, time elapsed since Christmas, and unsuccessful New Year’s resolutions. When those factors were combined and the “sadness” algorithm applied to them, 24 January 2005 was identified as the single most depressing of the year.

Almost immediately the claim was regarded by many as a shaky one because the cited factors were clearly vague and nearly impossible to quantify, and because of the dubious impetus behind the “formula.” The calculations were attributed to a Dr. Cliff Arnall of the University of Cardiff in Wales, who explained:

“Following the initial thrill of New Year’s celebrations and changing over a new leaf, reality starts to sink in,” Arnall said. “The realization coincides with the dark clouds rolling in and the obligation to pay off Christmas credit card bills.” The formula was devised to help a travel company “analyze when people book holidays and holiday trends,” said Alex Kennedy, spokesperson for Porter Novelli, a London-based PR agency. It seems that people are most likely to buy a ticket to paradise when they feel like hell. “People feel bleak when they have nothing planned, but once they book a holiday they have a goal, they work toward having time off and a relaxing period,” Kennedy said.

If that sounded a bit like a paid placement by a public relations firm working on behalf of a travel company to increase vacation sales, it’s because the “research” was exactly that. By 2006, Blue Monday’s roots in public relations had been fully exposed via others working in scientific fields who’d been offered the same financial opportunity as Arnall (who was a part-time tutor for night students at the time):

In fact it’s not surprising that these equations are so stupid, because they come from the PR companies almost fully-formed and ready to have your name attached to them. I know that because I have received an avalanche of insider stories — Watergate it isn’t — including one from an academic in psychology who was offered money by Porter Novelli PR agency to put his name to the very same Sky Travel equation story that Arnall sold his to. In amongst their aggressive pitch they described how the story would go. “Blue Monday — January Blues Day is Officially Announced: The 26th of January is the most depressing day in the calendar for the majority of Brits as measured by a simple mathematical formula developed on behalf of Sky Travel. “By taking into account various factors such as avg temperature (C), days since last pay (P), days until next bank holiday (B), avg hours of daylight (D) and number of nights in during mth (N), we create a formula such as C(P+B) N+D. This formula allows us to work out the day with the highest ‘depression factor’ which you can then use as a focus for making things better, booking your holiday etc …” This is almost exactly as it was when Arnall revealed his important work to the world.

Arnall later followed up with a corresponding “happiest day of the year” formula, sponsored by the Wall’s ice cream company. In the intervening years, journalists and mental health professionals have taken Arnall to task for minimizing the issue of clinical depression. He later commented on his involvement with PR-as-science, amusingly objecting to other people’s fabricating information to promote a claim:

Despite criticism of his decision to accept money from PR firms, he insisted he had no regrets; in the past five years, he has earned a total £1,650 for identifying the two dates. “There was one comment that I had bought a really big house out of the proceeds,” he said. “People just make this stuff up.” He added: “I was originally asked to come up with what I thought was the best day to book a summer holiday but when I started thinking about the motives for booking a holiday, reflecting on what thousands had told me during stress management or happiness workshops, there were these factors that pointed to the third Monday in January as being particularly depressing … but it is not particularly helpful to put that out there and say ‘there you are’ … it is almost a self-fulfilling prophecy that it is the most depressing day.”

While the initial Blue Monday PR campaign has long since concluded, the belief any one day in January is particularly or significantly the most depressing took on a life of its own. Not surprisingly, the claim has been repeatedly recycled by other companies seeking to promote goods or services in the post-holiday winter period. And as social media became increasingly influential, the rumor evolved from a formula based on circumstances to an analysis of words used in tweets:

Blue Monday was originally identified in 2005 by academic Cliff Arnall, who thought it fell on the last full week of January. He calculated the date using a variety of factors including weather conditions, debt levels, failed New Year’s resolutions and the number of days that had elapsed since the end of the Christmas holidays. But over the past three years, researchers analysed more than 2 million tweets posted by Britons in January looking for negative language and phrases indicating a drop in mood. They found that today, there will be nearly five times the average number of tweets relating to guilt, as people abandon their promises to pursue a healthier lifestyle.

In 2014, the Blue Monday story was reincarnated and harnessed by “researchers” linked with (among other interests) an alcohol company, law firms, and a bottled water brand.

In short, the specifics behind claims about January’s hosting the most depressing day of the year have shifted, but the idea both originated with and is mainly advanced by marketers and public relations firms. No studies or evidence have proved any one calendar date is more gloomy than any others, and the formula linked with the calculation of such a date has no real scientific basis. Critics have noted that assigning arbitrary or transient causes (such as the arrival bills or the end of Christmas vacation) to clinical depression could adversely impact its sufferers by tacitly suggesting the condition is treatable through methods as simple as booking a vacation or buying a drink.