But Jon Cousins, founder of the depression-fighting website Moodscope.com says that the aim in releasing the results is to enlighten, not depress.
"On the face of it, discovering that today is one of the year's gloomiest could be seen as yet more bad news, but we like to think that forewarned is forearmed," the Daily Express quoted him as saying.
"See it like a weather forecast. If you knew it was going to be cold and wet, you'd take a coat and umbrella when you went out.
"Knowing that people's moods are likely to be low on January 3 suggests you should do what you can to look after your own well-being and expect others to be a bit glum that day, too. Cut them some slack," he added.
The UK's most unhappy day last year was Sunday March 20, when only 19.9 per cent of people described themselves as happy, narrowly followed by Monday January 3 (21.4 per cent) and Sunday December 4 when 21.6 per cent said they were happy.
While the happiest days of 2011 included Saturday August 27 when 52.9 per cent of Britons enjoyed fine Bank Holiday weather and Tuesday March 15 (48.4 per cent) and Saturday October 1, when 48.3 per cent of people asked said they were happy.