Nazi dictator Adolf Hitler greets supporters at a May Day gathering in the Olympic Stadium, Berlin. (Photo by Keystone). 1st May 1938

A reveller walks through the streets in the early hours during traditional May Day celebrations in Oxford, Britain, May 1, 2015. (Photo by Dylan Martinez/Reuters)

Students from the University of St Andrews jump into The North Sea, as a good luck tradition before exams start on the East Sands in St Andrews, Fife, Scotland on May 1, 2018. (Photo by Derek Allan/Alamy Live News)

Fifty years ago, as France exploded in mass protests, words scrawled on the walls of the Sorbonne summed up the revolutionary zeal of the time: “Run free, comrade, we’ve left the old world behind!”. Sexual liberation, artistic creativity and anti-capitalism were the order of the day. For those who were there, it was an unforgettable time. Here: A wounded student is transported by first-aid workers during riots on the Boulevard Saint-Michel, Paris, France on May 6, 1968. (Photo by Gökşin Sipahioğlu/SIPA Press)

Actor George Clooney is arrested with his father Nick Clooney (2R) during a demonstration outside the Embassy of Sudan March 16, 2012 in Washington, DC. United to End Genocide, the Enough Campaign and Amnesty International held a rally to call on the United States and world leaders to stop the violence in South Sudan and prevent hundreds of thousands of people from starving. (Photo by Win McNamee/Getty Images)

A Tyrannosaurus Rex dinosaur costume runs on the field as young boys play an exhibition soccer match during halftime of the MLS soccer game between the Los Angeles Galaxy and Seattle Sounders FC in Carson, California May 26, 2013. The dinosaur was on the field to promote the Natural History Museum of Los Angeles County. (Photo by Danny Moloshok/Reuters)

Andrew Profilli of Australia bleeds from the head during his 93kg bout against Priscus Fogagnolo of Australia during CFC 18 at Luna Park on August 26, 2011 in Sydney, Australia. (Photo by Ryan Pierse/Getty Images)

Hotel ushers pose for a photo at Tiananmen Square as delegates attend the second plenary session of the National People's Congress (NPC) in Beijing, China, March 9, 2018. The CPPCC is the top advisory body of the Chinese political system and runs alongside the annual plenary meetings of the 13th National People's Congress (NPC), together known as “Lianghui” or “Two Meetings”. (Photo by Jason Lee/Reuters)