It starts at night and runs until sunrise. You get to dance to the coolest music in the warm tropical nights. If you get tired you buy a reggae bed (a flattened cardboard box) and have a nap. Life doesn't get more chilled.
It's usually held in Jamaica but in 2009 it is going to be in Florida (USA) and Brazil - not sure why, see
www.reggaefestivalguide.com/