From ShipIt Days | Atlassian:
ShipIt
24 hours to innovate. It's like 20% time. On steroids.
That's, um, nothing like 20% time.
Though, of course, 20% time was never 20% time either:
Yahoo CEO and formal Googler Marissa Mayer once bluntly denied its true existence.
"It’s funny, people have been asking me since I got here, 'When is Yahoo going to have 20% time?'" she said on stage during an all-employee meeting at Yahoo. "I’ve got to tell you the dirty little secret of Google’s 20% time. It’s really 120% time."
That said, I think I'd take 10% time:
"It's not technically something that gets formal management oversight — Googlers aren't forced to work on additional projects and there are no written guidelines about it. Typically, employees who have an idea separate from their regular jobs will focus 5 or 10% of their time on it, until starts to "demonstrate impact." At that point, it will take up more of their time and more volunteers will join, until it becomes a real project." [attributed to "Google HR boss Laszlo Bock"]
Interesting final quote from Bock: "[The informal 20% time policy] operates somewhat outside the lines of formal management oversight, and always will, because the most talented and creative people can't be forced to work."
The interesting lesson is that you win when you convince your employee to produce more work. Maybe 20% time isn't such a bad idea for either side of the management fence. X hours of required work versus 1.2X of work the employee actively wants to give. Sounds like a win-win.