Leo II was crowned Emperor of Rome at just seven years of age.
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Charity song 'That's What Friends Are For' hit No. 1 on the Billboard Hot 100.
Massachusetts's Marconi Wireless Station Site successfully sent the first radio transmission between the US and Europe.
The Paris Peace Conference began in France.
NASA's Ingenuity helicopter took off for its 72nd and final flight on Mars.
The lie detector, invented in 1921 by John Augustus Larson, was first used in the Netherlands.
