The Australians invented duna days and turned it into an artform

We call them duvet days, mental-health days, employer-funded recreational time out. It's pulling a sickie. You call in sick when you just can't be bothered facing the world at work.

Some companies write a couple of duvet days into employee contracts. They don't mind if you're honest, or quiet, about it.

A Gisborne man has learned, though, that the secret to getting away with it is keeping it all on the down-low. His downfall was Facebook.

This bloke worked at a training institute and had asked for a week of unpaid leave for a waka ama championship, but the boss was short-staffed and could give him only three days off. Come Monday, the worker called into work sick with a damaged calf muscle. By Wednesday, the boss was looking at pictures on Facebook of the worker happily enjoying life at the waka ama competition.

The boss sacked him and the Employment Relations Authority has ruled that the sacking was justified for misuse of sick leave.

It did not accept his reasons that he should be able to manage his health as he saw fit and that his "spiritual being" was better away with the family than being miserable at home.

If he was sick, he should have been at home recuperating. If he was fit, he should have been at work and should not have tried to pull one over the boss.

Bosses get suspicious of people who call in sick when they have been refused leave, or who regularly don't turn up for work on Fridays or Mondays. Social-media sites such as Twitter and Facebook are good research tools for their investigations.

If bosses and their staff are honest, this situation shouldn't arise. The worker says "I'm mentally had-it" or "I need a day to clean my golf shoes"; a reasonable boss is likely to say, "We can't make Wednesday work, but have Friday off."

If you have a less-than-understanding boss, though, and it's really a choice of a duvet day or being "overly honest", the experts suggest you don't go near social network sites while you charge the emotional batteries. And maybe you can get away with picking up some essentials at the supermarket or getting a DVD, but don't zip into town for a new pair of shoes. Just in case.