I read this over at Law and Gospel.

I think the idea of Earth Hour is great and is something that we all should participate in! Join with people around the world for the care of our creation. For one hour this Saturday March 29th at 8:00pm turn off your lights and make a big impact on the world. This video from the World Wildlife Federation explains everything that you need to know.
Major cities around the world will join us in taking a stand on the greatest threat our planet has ever faced, uniting millions of people to turn the tide on global warming.