It's that time of year when China's censors heave on their marigolds and bring out the brillo to scrub the Chinese internet of any mention of Tiananmen Square.
But on Wednesday, the world is marking a quarter of a century since the massacre of students in the Beijing Square, and to keep the Chinese internet silent, the censors have brought out the industrial-strength bleach.
The censorship on social media is cleansing any mention of the day the Chinese People's Army turned the tanks on students and bystanders.
Users of Weibo, China's version of Twitter, have seen the words "National Amnesia Day" and "June 4th" banned, but even generic words like "remember", "today" and "tonight" are being wiped. Searches for '25', '25 years' pr 'square' “have also been blocked, according to Reporters Without Borders. China's version of Wikipedia, Baike, now has no mention at all of the entire year 1989.
Weibo users have used clever tactics to evade automatic censors in the past, referring to the 35th of May, instead of 4th of June. This year, emoticons are being used, like faces with tears or candles, but messages are regularly blocked.
"The censors have been far more successful this year than ever," said Kristyan Benedict, Amnesty's campaign manager. "I looked at the research done for the 20th anniversary and what the censors did and how many people were arrested. It was nothing like this."
This year, the Chinese authorities are a step ahead, Benedict said. "You can guarantee that whatever proxies the activists are using, whatever codes, whatever technology, the authorities have it but ten times better," he told HuffPost UK.
"There are new codes emerging, like people '89June425', that might sneak past but they are generally on top of everything."
"China sees the Internet as an ideological battlefield," Hong Kong activist and blogger Oiwan Lam said in a post.
"The range of the censored terms– names related to the Tiananmen event, the party's historical internal struggle, and Hong Kong contemporary politics – shows just how sensitive the Chinese Communist Party still is about the 1989 Tiananmen Square Massacre, and the extent it is willing to go to make sure that no one talks about it."
Google’s transparency report showed lower levels of activity from China starting from about Friday, which could indicate a significant amount of disruption, according to the New York Post. Other Western sites are also being slowed down or blocked, Benedict said.
"If you're savvy, you can get past the censors, but that's no way to start a mass movement, you will only ever reach a tiny minority of people with your message if you are posting on forums under a pseudonym using a proxy."
But some Western internet companies are actively helping too, according to Global Fire which monitors censorship in China.
Writing under a pseudonym, Xia Chu alleged the Microsoft-owned search engine Bing was more aggressively blocking than Baidu, the leading Chinese search engine.
According to Quartz, the search engine even blocked a picture of this cute dog from a Chinese cartoon. Because he's sitting on a tank.
Bing told the website it was constantly reviewing what had been removed.
Last year, a variety of other memes surfaced to mark the day. Most famous was the yellow duck meme, with the tanks in the famous 'Tank Man' picture being erased and replaced with pictures of the giant blow-up duck that had sat in Hong Kong's harbour. The words 'yellow duck' were banned from social media in response.
It means that activists' work must move offline, according to Benedict. Last year, people on Weibo were being told to wear black and also to light candles outside their homes to remember the victims. The words 'black' and 'candle' were promptly erased from the site.
But those who would start an offline movement have also been pre-emptively scuppered. Around 66 activists have been pre-emptively detained by the Communist Party regime, including Luo Xi, a student activist in 1989 And Bao Tong, 81, a former political aide to the late Communist Party leader Zhao Ziyang, who opposed the crackdown in 1989. Many more had been warned to leave Beijing before the anniversary, Amnesty said.
Guo Jian, a prominent Chinese- Australian artist and former Tiananmen Square protester was taken away on Saturday night from his home at the Songzhuang art colony in eastern Beijing.
Guo had recently revealed in an interview with the Financial Times that he had created a large diorama of Tiananmen Square with 160 kilograms of minced meat.
The most recent research appears to indicate that the Orwellian quip 'Whoever controls the past controls the future' is working in China. A third of China's population was born after the massacre. Only 15 out of 100 Beijing students recognised the iconic picture of “Tank Man”, according to Louisa Lim, in her book The People’s Republic of Amnesia.
One place where the massacre is not forgotten, or censored, is Hong Kong, where organisers expect 150,000 for a candle-lit march through the street. In London, 25 Tiananmen Square survivors and other dissidents will go to the Chinese embassy in London, dressed in black, with Amnesty International UK Director Kate Allen, to lay red roses. Laying the flowers at the embassy will mean the commemoration will take place on official Chinese territory. In the midst of vice-like clampdown, that's about as defiant as you get.