You might have heard of Google's 20 per cent time, but do you know what it actually is? And why it's so important? Google allows employees to devote 20 per cent of their working time to projects they're passionate about.

"Usually what people use that for is to research and investigate ideas they come up with and start to develop them to the point where they can actually launch them," Google's Nick Creswell, University Programmes Manager and cultural guru, tells TechRadar.

And, culturally, the concept is an integral part of Google. "Everybody's really involved. It's something that's owned by everyone in the company, particularly in the software engineering functions," continues Creswell.

"20 per cent time is something that we've had pretty much since the organisation was founded. It's been one of the major drivers of innovation."

Projects from 20 per cent time

Creswell cites the examples of Gmail, Google News and the less successful Orkut as projects borne out of the 20 per cent time concept. "Gmail was completely unconnected to anything Google was doing [at the time] when the engineer came up with it," says Creswell.

And then there's the flight simulator in Google Earth, also invented by an engineer working on his 20 per cent time.

"He's a real flying enthusiast. Before he worked at Google he was working on flight-related software. He still has a real passion for flying. And it's a real favourite among flight aficionados. I think that's a really good example."

There's also Google Accessible Search, started by a blind Google employee. "He's been working on a search engine specifically for the visually impaired. Its search ranking is based on sites that are particularly easy to read – also pages that are based on a very clear design are further up, so that people who are partially sighted or visually impaired can access more relevant results." Clever stuff.

Who can do it?

So who can take advantage of 20 per cent time? "Anybody working on any kind of project can come up with a new idea and they can basically use that time to test the feasibility of it," says Creswell. "They might end up joining up with other engineers who also dedicate their 20 per cent time to the same kind of idea, so that it can gradually build up momentum around the idea so that it can become an new project, or a new feature on a project."

And it doesn't have to be at all connected to their day job. "It can be absolutely anything, so it can be directly connected to what they work on day to day, or it can be a completely different area. A number of people use it to investigate a project that they might be thinking of working on full time, so they use that time to find out more."

There aren't any formal restrictions on 20 per cent time, it works on trust, although Creswell was quick to point out that people bounce ideas off each other and sanity checks from managers are in place.

How many Googlers?

Google says it doesn't know how many of its employees are on 20 per cent time: "As it's not structured it can be difficult to track" said a spokesperson, while employees are not specifically remunerated for extra time they may have to spend working on their day jobs.

Employees are left to gauge their own ability to spare time. "We deliberately don't have specific guidelines around it. In some way it needs to relate to Google's broader mission of organising the world's information and make it useful and accessible," adds Creswell.

The aim of 20 per cent time doesn't necessarily have to be completely product focused, either. One of Creswell's colleagues is using their 20 per cent time to develop better relationships with universities.

"We have a culture of delegating responsibility to individuals, the engineers who are at the coal face, who know what needs to be developed. It's the individual satisfaction that comes out of it."