China has put pro-democracy activists under house arrest ahead of the 33rd anniversary of the 1989 Tiananmen massacre, while the strict suppression of June 4 commemorations of victims has spread to once-free Hong Kong, now under mainland-style authoritarian rule. But with the student protesters now well into their 50s, and children born since the killings being raised with scant knowledge of the event, the passage of time is helping the Communist Party erase memories.