Candle Night Summer Solstice 2007. Turn out your lights for two hours on the Summer solstice, June 22nd, eight to ten p.m.
Do something special-Read a book with your child by candlelight. Enjoy a quiet dinner with a special person.
This night can mean many things for many people.
A time to save energy, to think about peace, to think about people in distant lands who share your planet.

Pulling the plug open the window to a new world.
Awakens as to human freedom and diversity.
It is a process, finding a larger possibility of the human civilization.
By turning off lights for only two hours, we will be all loosely connected.

Let’s make a “wave of darkness” spread over the globe together.
On the evening of Summer solstice, June 22nd, for two hours from 8 to 10 p.m. Turn out your lights, take it slow.

Source.

This site was translated rather well from Japanese (where the idea originally came from), and even has tips on how to enjoy Candle Night.

Mari loves participating in stuff like this, so naturally Mari will be using candles or maybe even fireflies on the night of the summer solstice. You should all try this too!