The largest environmental event in history - Earth Hour - is set for March 23. All you have to do to participate is switch off your lights between 8: 30 p.m. and 9: 30 p.m. on Saturday. In 2012, more than 6,700 cities and towns in 152 countries took part in Earth Hour, which is meant as a call to action on climate change. The World Wildlife Fund started Earth Hour in Australia in 2007. More than 2.2 million took part. In 2008, the rest of the world, including Canada, joined in and now it's a global movement. For information on Earth Hour in Canada, see wwf. ca/EarthHour
