March 31, 2012 at exactly 20:30 local time, hundreds of millions of people will turn off their lights for one hour to show they care about the future of our planet. This action is called "Earth Hour 2012".
This campaign is to make an important contribution to the efforts to save energy and rescue the planet. In many cities around the world will go dark for an hour billboards, windows, offices and apartments.
In 2011, this event was attended by 5,200 cities in 135 countries.
The campaign is the World Wildlife Fund.