As you may know, today is Blue Monday, the most depressing day of the year.

Have you felt a bit listless since you heard?

Has Blue Monday caused you to gaze wistfully out the office window, longing for white sand and rolling azure waves in some far away paradise?

Perhaps that's because someone intended you to.

Reading many newspapers and websites today, you might assume that some crack team of scientists - boffins perhaps - have calculated endless variables and arrived a mathematical proof to show the third Monday of every year is the most depressing date.

There is in fact such a mathematical proof, and here it is below:

                [W + D – d]T^q/MN_a

W=weather, D=debt, d=monthly salary, T=time since Christmas, Q=time since failing our new year’s resolutions, M=low motivational levels, and N_a=the feeling of a need to take action.

Now it may have been some time since the Leaving Cert, but you'll surely have noticed that this looks neither very mathematical nor very scientific.

Blue Monday, and the formula above, are in fact an invention of a PR firm working for the now-defunct Sky Travel.

Both were proposed to British psychologist Dr Cliff Arnell, who attached his to give the campaign credence. Arnell also identified the year's 'happiest day' for Walls ice cream, which falls in mid-June. For both, he claims to have earned €2,155 (£1,650) 

Guardian science columnist Ben Goldacre debunked Arnell's claims eight years ago in a scathing article, in which he derides such equations, which "come from the PR companies almost fully-formed and ready to have your name attached to them."

Arnall himself has asked the public to ignore his work, saying the formula is "not particularly helpful" and a "a self-fulfilling prophecy."

So cheer up. There's only one true Blue Monday.