Taiwan called on China to officially acknowledge the 1989 Tiananmen crackdown on Thursday, as the island marked the anniversary of the day student-led protests were violently crushed by tanks.
Hundreds of people were killed during the Communist Party's suppression of demonstrations calling for democratic reforms.
But open discussion of the incident is forbidden on the Chinese mainland, with censors scrubbing mentions of protests, and dissidents often visited by police in the days leading up to the June 4 anniversary.
"Around the world, there are 365 days in a year. Yet in China, one of those days is purposely forgotten each year," Taiwan's President Tsai Ing-wen said on Twitter.
Tsai said Beijing needed to confront the legacy of the incident, just as Taiwan had been forced to reckon with its own authoritarian past before its transition to democracy in the 1990s.
"There were once days missing from our calendar, but we've worked to bring them to light. I hope one day China can say the same," she wrote.
Tsai's comments came a day after the Mainland Affairs Council called on Beijing to offer "sincere apologies" over the Tiananmen crackdown.
China's foreign affairs ministry derided the comments, which spokesman Zhao Lijian described as as "complete nonsense" on Wednesday.
Tensions between Taipei and Beijing have surged since Tsai was elected in 2016 because her government considers the island to be a de facto independent state rather than an unincorporated Chinese territory.
Taiwan has long marked the date of the Tiananmen crackdown with solemn vigils mourning the dead.
The ceremonies are usually dwarfed by much larger gatherings in Hong Kong, the only place in China where such mass displays of remembrance are possible.
But this year's memorial in the finance hub was cancelled by authorities citing the need to halt the spread of coronavirus.
Taiwan has welcomed an influx of Hong Kong residents who have moved to the island out of fear their city's unique liberties were slowly being extinguished by Beijing.
Tsai pledged humanitarian assistance for Hong Kongers after Beijing's parliament rubber-stamped plans outlining a new national security law for the finance hub.