Why is Blue Monday today and what was the formula used to work out the ‘saddest day of the year’?

JANUARY 21 has been declared Blue Monday in 2019 - and it's been coined "the most depressing day of the year".

In 2005, Dr Cliff Arnall worked out how a variety of factors  - including debt and weather - come together in perfect sync on a certain Monday in January of every year.  Here's how it was worked out as the "saddest day".

Who is Dr Cliff Arnall?

According to , Dr Arnall is not the Cardiff University psychologist he is sometimes described as - he actually taught evening classes at the university's affiliated adult education centre.

The Welshman is from Brecon in Wales, and also refers to himself as a "freelance happiness guru".

When is Blue Monday 2018?

It's been calculated that Blue Monday 2018 will be January 21 (TODAY) using the formula below.

The date is generally reported as falling on the third Monday in January, but can also be on the second or fourth Monday, or even the Monday of the last week of January.

The first one was January 24 in 2005.

Is Blue Monday real?

Despite some very official-looking algebra, Blue Monday was actually invented by Sky Travel in a bid to boost summer holiday bookings.

In 2010 Dr Arnall revealed that he had simply picked a date when asked to work out the most depressing day of the year.

He said: "I was originally asked to come up with what I thought was the best day to book a summer holiday.

";When I started thinking about the motives for booking a holiday, reflecting on what thousands had told me during stress management or happiness workshops, there were these factors that pointed to the third Monday in January as being particularly depressing.

"But it is not particularly helpful to put that out there and say 'there you are' - it is almost a self-fulfilling prophecy that it is the most depressing day."

However the January Blues are a very real medical condition, that often happens after Blue Monday.

What has he said recently about his discovery?

In 2018, Dr Arnall has teamed up with another travel company - Virgin Atlantic - to try and reclaim Blue Monday.

The new angle is for Blue Monday to be used as a day of planning what direction you want the next twelve months to take you on.

: "Whether embarking on a new career, meeting new friends, taking up a new hobby or booking a new adventure, January is actually a great time to make those big decisions for the year ahead.”