National holidays are usually set well in advance. So when Beijing abruptly announced an extra three days of official holidays in early May, schools and businesses had to scramble to accommodate the new schedule.

The sudden change is just one of the measures the Chinese capital has taken to make sure no untoward gatherings are held to mark the 100th anniversary of the May Fourth Movement, which spurred the modernisation of Chinese politics and society. It is followed by the even more sensitive 30th anniversary of the June 4 1989 military suppression of student and worker protests on Tiananmen Square.

Songs have been taken off music streaming platforms and controls on academics tightened ahead of the two anniversaries. To prevent any possible unrest, China extended the May 1 national holiday from one day to three days in the hope that many residents take vacation outside the capital.

“Both anniversaries are still very relevant today. The Chinese are big on anniversaries and the centennial of the May 4th Movement is a big deal indeed,” said Kin-ming Liu, a senior Hong Kong-based journalist and editor.

The Communist party regards itself as the natural heir to the May 4 movement, in which students demonstrated for a strong China that could stand up for itself on the international stage against colonial powers. On Friday, president Xi Jinping sought to hitch the legacy of the May 4 movement to his own signature political slogan. He urged the party to study the May 4 movement and “motivate young people to make unremitting contributions to national rejuvenation.”

However, the party is far more wary of the movement’s other themes, including feminism, artistic freedom and calls for democracy. Of the Tiananmen Square protests, the party prohibits any commemoration.

Anniversaries . . . are important because they can open up space for gatherings and for discussions of the past that can easily incorporate criticisms of the present

“Anniversaries, especially of events that the authorities see as worth marking, are important because they can open up space for gatherings and for discussions of the past that can easily incorporate criticisms of the present,” said Jeffrey Wasserstrom, professor of Chinese history at University of California, Irvine.

“A central conundrum of today’s China is that the authorities seem to have things well under control, yet remain twitchy [about any potential for discontent],” he added.

Students demonstrating on Tiananmen Square in the spring of 1989 commemorated the anniversary of the protests of May 4 1919, creating a direct link between the two movements. Both were in defence of students’ right to protest and intellectual freedoms against governments determined to shut down popular expression.

A protester stands before a line of tanks on Tiananmen Square in June 1989. Authorities are wary of the 30-year anniversary of the protests and the military crackdown that followed © AP

Last month, the prestigious Peking University summoned its professors for a lecture on “tightening up the Communist party’s management and strengthening the faculty’s moral construction” — a clear message not to step out of line.

Peking University students were among the most active in 1919 and 1989, as well as in most of the other student movements of the past century.

But after years of tightening controls on academics and public intellectuals, the Communist party today is just as worried about leftists as it is about liberals.

In the past month, at least two prominent Tsinghua academics — one a liberal critic of Mr Xi, the other a professor of Marxism — have come under attack. The first, Xu Zhangrun, was suspended after he wrote an essay that criticised the removal of term limits that allows Mr Xi to be president for life.

The second, Lu Jia, was denounced by ultra-leftist students using Cultural Revolution terminology for what they said were his failings on Marxist ideology.

Authorities have also cracked down on one of the few student movements to gain any traction since Mr Xi came to power — a group of young Marxists agitating for better working conditions in southern China.

The nervousness has spread to popular culture, with Apple Music and Tencent’s QQ removing songs that reference student demonstrations from their streaming services. Apple declined to comment.

At least one musician’s fans are fighting back. Last week, after singer Li Zhi's social media account was wiped out and his ballads removed from streaming services, devoted netizens changed their profile photo to his in a subtle protest.

Copyright The Financial Times Limited . All rights reserved. Please don't copy articles from FT.com and redistribute by email or post to the web.