On Saturday, March 29, 2008, Earth Hour invites people around the world to turn off their lights for one hour – from 8:00pm to 9:00pm in their local time zone. On this day, cities around the world, including Copenhagen, Chicago, Melbourne, Dubai, and Tel Aviv, will hold events to acknowledge their commitment to energy conservation.
[From Google]
We observed it here in Seattle. Even the big light towers at our local sports park went off at the stroke of 8. It was interesting to sit around by candlelight . . . .