You'll notice something "off" about the homepage tomorrow â€" our lights! On Saturday, March 27 th from 8:30pm to 9:30pm local time, the World Wildlife Fund invites you to join people from 3,100 cities in 121 countries on all 7 continents in participating in Earth Hour , where people across the world can demonstrate their concern about global climate change with the simplest of gestures: turning off all non-essential lights and electronics.