On April 25, 1976, at Dodger Stadium, father-and-son protestors ran into the outfield and tried to set fire to a U.S. flag. When Cubs outfielder Rick Monday noticed the flag on the ground and the man and boy fumbling with matches and lighter fluid, he dashed over and snatched the flag to thunderous applause. When he came up to bat in the next half-inning, he got a standing ovation from the crowd and the stadium titantron flashed the message, "RICK MONDAY... YOU MADE A GREAT PLAY..." Monday later said, "If you're going to burn the flag, don't do it around me. I've been to too many veterans' hospitals and seen too many broken bodies of guys who tried to protect it."

When did protesters run into the outfield and try to set fire to the U.S. flag?