When is the day when the earth lights out for one hour?

"Earth Hour" is a global energy-saving activity proposed by WWF in response to global climate change. It is proposed that every year at 20:30 pm local time on the last Saturday of March (20: 30 pm Earth Hour time in 2020), households and business users turn off unnecessary lights and power-consuming products for one hour to show their support for climate change action.

The "Earth Hour" event was first held in Sydney, Australia on March 3, 2007, and attracted more than 2.2 million families and businesses in Sydney. Subsequently, the activity quickly swept the world at an alarming rate.

The purpose of "Earth Hour" is not to save electricity, but to make the public aware of the importance of protecting the earth, improve environmental awareness and form good environmental habits in daily life.