January 21 is supposedly this year’s Blue Monday, the most depressing day of the year. But most scientists will tell you not to believe the hype -- the whole concept is purely a public relations tactic originally used to sell vacations.

Supposedly the third Monday in January is especially gloom-inducing when you factor in the weather, debt, time since the holidays and motivation levels. The first Blue Monday was announced in 2005 by a travel agency called Sky Travel, with the added hint that perhaps mid-January would be the perfect time to book a spirit-lifting vacation.

There’s some appealing logic behind Blue Monday. We’re deep in the dog days of winter, with spring still an unimaginable two months off. Winter depression, or seasonal affective disorder, is a very real thing, thought to possibly stem from neurotransmitter imbalances or a lack of Vitamin D.

Meanwhile, the fervor of the holidays has curdled into bills due and party food-induced chub that, despite our fevered New Year’s resolutions, is not instantly melting off.

And Mondays really can be the worst -- one 2009 paper from a Japanese team of researchers at Showa University looked at statistics for all suicides in Japan in the year 2003. Men of all ages were more likely to commit suicide on Mondays, it turns out.

But many commentators argue that putting these factors into a formula to designate a single day as the most depressing one of the year for everyone is silly pseudoscience.

Ben Goldacre, a science writer for the Guardian, points out that the supposed father of the Blue Monday equation, Cliff Arnall, has attached his name to several equally silly press release-ready formulas, like ones for “happiest day of the year” and the perfect long weekend.

“In my more extremist puritanical moments, I am of the opinion that these equation stories -- which appear with phenomenal frequency and make up a significant proportion of the total science coverage in the UK - are corrosive, meaningless, empty, bogus nonsense that serve only to caricature and undermine science,” Goldacre wrote in 2006.

For instance, Arnall’s equation for the perfect long weekend makes little sense, Goldacre points out. The formula involved dividing time spent on activities by travel time and delays. So, according to the formula, one could have an infinitely good weekend by staying home and cutting travel time to zero, since dividing things by zero equals infinity.

Staycations are nice enough, but really, how often do you achieve Nirvana when you’re Netflixing “Doctor Who” in your pajamas on a Thursday afternoon?

“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,” Goldacre wrote.

The entire press release with the Blue Monday equation that eventually was put out under Arnall’s name was offered to a number of academics by a public relations firm, according to Goldacre.

Arnall’s equations for happy and depressing days might get more traction because he is usually described in the press as a psychologist from Cardiff University.

“To be a Cardiff University psychologist, you usually have to be employed/publish research from Cardiff School of Psychology, hence I can claim to be one,” actual Cardiff psychologist Dean Burnett griped in the Guardian last year. “Dr. Arnall briefly taught some psychology-related evening classes at the university's adult education center. Apparently, this makes him a Cardiff University psychologist. Using that logic, I'm [a grocery store] manager, because I once made one of their staff fetch me a discount chicken.”