In an effort to conserve energy, Board of Supervisors President David Chiu introduced legislation yesterday that "would prohibit downtown commercial buildings from leaving the lights on after hours," according to reports. If passed, Chiu's idea would "require commercial building owners to phase in the darkened skyline over one year," which would make San Francisco the only city in North America to shut off their office building lights at night to converse energy. If your recall, Aaron Peskin introduced similar legislation last year, which failed after the Building Owners and Managers Association of San Francisco gave it a thumbs down.