The event started in 2007, when 2.2 million Sydney, Australia residents turned out their lights for an hour. It has been growing ever since and this year people worldwide are asked to put out any non-essential lights tonight from 8:30 until 9:30. That's local time, to be clear, so no worries about daylight savings or trying to figure out when sundown is in Australia.
There seems to be quite a bit of traction behind the event this year, with even Google getting in to the action. And we think you should too -- it's certainly easy enough. Just remember: only turn off the non-essential lights. Headlights definitely do not fall in that group. [From: My Earth Hour, via: Google, The Boston Globe]