WASHINGTON (AP) — Washington’s National Cathedral is among the landmarks across the globe that plan to turn out their lights for Earth Hour.

The cathedral’s lights are to be dimmed at 8:30 p.m. Saturday as part of the event organized by the Washington-based World Wildlife Fund.

The National Aquarium in Baltimore also plans to participate in the event designed to raise awareness of environmental sustainability issues.

The event begun in 2007 encourages people to turn off lights at 8:30 p.m. local time on Saturday. The World Wildlife Fund says people in 135 countries participated last year.

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