Finland officially joined NATO, becoming the 31st member of the security alliance.
Elon Musk bought a 9.2% stake in Twitter, amounting to $2.9 billion.
The 21st Commonwealth Games officially began on the Gold Coast, Queensland, Australia.
The Pink Star Diamond sold for a record USD 71 million in Hong Kong.
Beyoncé and Jay-Z married with only 40 guests present on their special day.
Jack Ma founded Alibaba Group Holding Limited.
NASA's Challenger Space Shuttle was launched from Florida on its maiden voyage.
Bill Gates and Paul Allen founded Microsoft.
New York City's Twin Tower World Trade Center was officially opened.
Martin Luther King Jr. was assassinated.
Adolf Hitler formed the Schutzstaffel, the infamous paramilitary organization known to most as the SS.
The Kangra earthquake in India killed over 20,000 people.
US Congress released a US flag that featured 20 stars and 13 red and white stripes.
The Declaration of Breda document was issued by the exiled King Charles II of England.
Moscow was mentioned for the very first time in historical records when two princes met there for a great banquet.
