Blue Monday is observed on January 18, 2021. This day falls on a day in mid-to-late January, stated to be the most depressing day of a year. Usually Blue Monday takes place on the third Monday in January, but may alternatively fall on the second or fourth Monday, or the Monday of the last full week of January. Blue Monday was first mentioned om 2005 either by Cliff Arnall, then tutor at the Centre for Lifelong Learning at Cardiff University, or by a travel company. The first published date was January 24. Scientists, however, declared the used formula that calculates the date of Blue Monday as nonsense.