Earth Hour 2013 is 8:30 p.m. Saturday, March 23

Earth Hour 2013 begins at 8:30 p.m. March 23 in your local time zone. Unfamiliar with the concept? The effort urges people around the world to turn off their lights for an hour to show concern for the environment. This is the seventh year of the campaign.

Some background on Earth Hour: "Earth Hour came from a think tank initiated by Earth Hour Executive Director and Co-Founder, Andy Ridley, resulting in the formation of a partnership between WWF Australia, Leo Burnett and Fairfax Media to address the climate change issue," according to the campaign's official website.

Here's a gallery of Earth Hour photos from around the world.

In Georgia news, Savannah's City Hall will go completely dark for Earth Hour, according to The Associated Press.