In 2003, several Japanese environmental groups urged people to turn off their lights for two hours on the night of the Summer Solstice and “to enjoy something different and unusual.” It marked the beginning of Candle Night. Approximately 5 million people participated in that first Candle Night, according to Japan’s Ministry of the Environment (MOE). The event was repeated on the Winter Solstice.

Since then, Candle Night—with its slogan of “Turn off your lights, and take it slow”—has grown, with many major Japanese landmarks and facilities also committing to turning off their lights.

The MOE holds a similar campaign to reduce CO2 emissions. Called Black Illumination, it takes place over several days around the time of the Summer Solstice. The MOE estimated that about 4,000 facilities participated in 2006, saving roughly 810,000 kWh of electricity. (The average U.S. household consumes about 10,000 kWh a year.)