For one hour every year, inhabitants of 7,000 cities across the world turn off their lights in support of environmental issues.
Despite becoming a global phenomenon, the initiative had humble beginnings as the brainchild of a British expat living in Australia.
Andy Ridley launched the idea from Sydney in 2007 and has since seen it grow into the biggest mass participation in the world.
It brings hundreds of millions of people together in a common cause for a brief period of time each year and has also led to a number of other big changes, reports the Telegraph.
Ridley told the news provider: "Earth Hour is symbolic of people coming together to unite for the sake of the planet. It has been hard work but we are now getting people to think beyond that hour."
The raised state of awareness around climate change as a result of Earth Hour has seen citizens lobby both governments and major corporations, resulting in some cases of laws being implemented.
Smaller changes, such as forests being planted and lightbulbs being replaced for energy-efficient alternatives have also occurred as a direct result of Earth Hour.
Originally from Norwich, Ridley moved to Australia in 2002, where he worked for WWF for ten years, before relocating to Singapore to run Earth Hour from Asia.
He credits being an expat as an important factor in the success of the project.
Ridley said: "Earth Hour was not a Western movement. It started in Sydney with no expectations or hype. And the fact it came out of nowhere was really important. I think if we started it in London it wouldn’t have worked."
Like many of the best ideas, Earth Hour began on the back of a beer mat in a Sydney hotel in 2006.
He worked alongside several other employees in its development, but was then given the mandate to run the turning the lights out element himself, which has since gone from strength to strength.
March 29th is the dates set for Earth Hour 2014, which will be held between 8.30pm and 9.30pm.
Be ready to switch your lights off!