Via Mhz visually & via Japan Today digitally:

25,000 facilities join lights-out event to save energy

Monday, June 20, 2005 at 07:05 JST
TOKYO — Some 25,000 facilities nationwide, including Tokyo Tower, had their lights turned off on Sunday evening in an event to help preserve energy.

The Environment Ministry and a nongovernmental environmental organization launched the event two years ago to urge people to turn off their lights for energy conservation. This year, the event will run until Tuesday, during which participants will turn off the lights for two hours from 8 p.m. (Kyodo News)

I’d like to try this in DC :)