This might be the key to getting more done at work. (Clue: It's not what you'd expect)

On Mondays, the week ahead can look incredibly long — but the idea of heading to work five days a week could soon be left in the past. At least that's what unions in the UK have been calling for recently.

According to a new study from Saïd Business School at the University of Oxford, a four day working week would actually be a great idea for productivity and employee happiness.

Over six months, associate professor of economics and strategy Jan-Emmanuel De Neve studied the happiness and productivity of 5,000 call centre workers from 20 BT offices. Workers were asked to rate their happiness every week on a scale from one to five.

The results showed how a four day week was correlated with more positivity, an increased number of calls made, and a better quality of calls when customer satisfaction was measured, the Telegraph reports. There were also fewer absences and more sales made.

This might suggest that having a three day weekend could improve work-life balance, as employees would have more opportunity to unwind, instead of feeling like they run out of time with the current system.

"I would argue the four day working week is spot on in terms of finding or striking that right balance between improving the work-life balance and unlocking the happiness potential from that in terms of productivity gains," De Neve told The Telegraph. "This outweighs the net reduction in productivity from working a day less."

An eight week trial conducted in New Zealand earlier this year between March and April found that overall, a four day week increased teamwork and work engagement, and decreased stress.

But there were some problems with the study, in that some people had to break out of the trial to keep up with a busy schedule — suggesting an extra day off could lead certain employees to pick up the slack.

There was no real improvement in work quality in the trial, but employees did enjoy having a three day weekend.

De Neve told The Telegraph this is a neurobiological effect of having a shorter working week.

"When you are more positive about your job and your life while on the job, it relates to being able to be more productive," he said.

There may not be an immediate change in productivity if a four day week was introduced, but it's definitely a possibility. With less time to kill, workers may procrastinate less, although there are always going to be those who try to take advantage.

More evidence is probably needed before we're likely to see a major adjustment to the way we work. However, it wasn't until the 20th century that businesses decided a five day week was optimum and changed Saturday into a day off, so there's no reason to believe it couldn't happen again.