Yesterday would have marked John Lennon’s 60th birthday, and the event did not go unnoticed around the world. Hundreds gathered to leave flowers, hug and strum guitars at New York’s Strawberry Fields monument in Central Park, only a few steps from the Dakota apartment building where Lennon lived (and was shot to death on Dec. 8, 1980 by Mark David Chapman, who last week was denied parole). In Los Angeles, some 200 people reportedly gathered around the late Beatle’s star on the Hollywood Blvd. Walk of Fame and sang “Happy Birthday” twice — once for Lennon, then again for his son Sean, 25, who shares the same birthday as his father. Sixty candles were placed on the star itself. In London, two Lennon solo albums were released, the re-issued “Double Fantasy,” with three extra tracks, and “John Lennon/Plastic Ono Band,” his first work after he and the Beatles split. Lennon’s widow, Yoko One, meanwhile, was in Japan yesterday to oversee a new Lennon museum, which flung open its doors for the public Monday. “I’m so happy that John’s 60th birthday is getting so much attention and love from people all over the world,” she said in a statement.