If Blue Monday is cited as the saddest day of the year, studies and algorithms suggest that there also is a day that has been labelled as the happiest of each year.

While this year's Blue Monday was on January 17, the happiest day of 2021 is Monday, June 20.

Yellow Day: Origin and why it is the happiest day

The date has been celebrated since 2005 when Cliff Arnall, who also invented Blue Monday, came up with the idea of looking for a mathematical formula that would also identify the happiest and most attractive day of the year.

This formula consists of factors such as the outdoors, nature, contact with others, positive memories, average temperature and the proximity to the holidays and, as a result, the day is usually at the beginning of every summer.

Meanwhile, many Spaniards considered yellow to be the colour that brings bad luck, but since La Roja won Euro 2008 donning a yellow shirt, many people have abandoned this superstition.