The first leap second was added to the UTC time system.
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Charles Blondin became the first person to cross Niagara Falls by walking across a tightrope.
Donald Trump became the first US president to visit North Korea while meeting Kim Jong Un.
An unidentified object thought to be a meteoroid or comet smashed into a remote forest in Siberia and destroyed 21,528 square feet of land.
Spain legalized same-sex marriage.
The Nazi Party killed around 1,000 people, which became known as the 'Night of Long Knives.'
