At 8.30pm on Saturday 23 March, one billion people will have their lights punched out.
This large-scale lights-out is Earth Hour, an initiative which started in Sydney in 2007 and today is a global phenomenon involving 4,000 cities. "We had this idea that turning the lights off would cause people to turn on their minds to issues of sustainability and climate change," says Earth Hour's creator Greg Bourne, CEO of WWF Australia.
Ten years since Sydney's millennial fireworks sparked the idea, Bourne's baby does much more than that - for many more people. "Global connectivity is really key in our thinking. If the lights going out in Sydney can be replicated around the world, catalysing important discussions and involving children, Earth Hour will make a difference."
Here are Time Out's tips on how to get involved...
Earth Hour is now the world's biggest environmental campaign, with the Sydney Opera House, Golden Gate Bridge in San Francisco, Times Square in New York and Rome's Colosseum all extinguishing their lights in support. "Switching off your lights is a great first step, but your true environmental impact is much bigger than just your energy bill," says Bourne. "We want to make Earth Hour every hour."
"Each individual's environmental impact - or environmental footprint - is made up of things such as the food you eat, the transport and housing you choose, and the goods and services you buy," says Bourne. "This year we're encouraging people to use our footprint calculator to see just how sustainable their lifestyle is."
Cento in Melbourne sources all its food within 100km and Billy Kwong in Sydney is a carbon neutral restaurant. Bourne recommends home chefs buy in-season produce that doesn't need to be transported around the world "or take a leaf out of your grandmother's book and use a hot post-roast oven to warm a dessert."
"Doing small things around the house can make a big difference. Change to rechargeable batteries, or recycle normal batteries for the zinc. Turn things off rather than on standby."
"Double the efficiency of your car," says Bourne. "Put another person in it!"