Birthday of Carl Gustaf Emil Mannerheim & Flag Day celebration of the Finnish Defence Forces (Finland)
Crane Driver's Day in Russia (or Crane Operator's Day is an unofficial holiday)
Hug Your Cat Day in US
June 4th revolution in Ghana (1979)
National Cheese Day in USA (52% of Americans believe cheeses are interchangeable in recipes, and 28% say they switch cheeses because they like to experiment with the flavors different cheeses offer)
National Cheesemakers Day in US
National Healthcare Recruiters Day in US
National Unity Day in Hungary
Old Maid's Day
Tiananmen Square Protests of 1989 Memorial Day (International)
Tonga Emancipation Day or Independence Day (Can be moved to a Monday. Commemorates the abolition of serfdom in Tonga by King George Tupou in 1862, and the independence of Tonga from the British protectorate in 1970)
World Caries Day
1996 – The first flight of Ariane 5 explodes after roughly 37 seconds. It was a Cluster mission.
1989 – Solidarity's victory in the first (somewhat) free parliamentary elections in post-war Poland sparks off a succession of peaceful anti-communist revolutions in Eastern Europe, leads to the creation of the so-called Contract Sejm and begins the Autumn of Nations.
1986 – Jonathan Pollard pleads guilty to espionage for selling top secret United States military intelligence to Israel.
1975 – The Governor of California Jerry Brown signs the California Agricultural Labor Relations Act into law, the first law in the U.S. giving farmworkers collective bargaining rights.
1961 – In the Vienna summit, the Soviet premier Nikita Khrushchev sparks the Berlin Crisis by threatening to sign a separate peace treaty with East Germany and ending American, British and French access to East Berlin.
1944 – World War II: A hunter-killer group of the United States Navy captures the German submarine U-505: The first time a U.S. Navy vessel had captured an enemy vessel at sea since the 19th century.
1944 – World War II: Rome falls to the Allies, the first Axis capital to fall.
1940 – World War II: The Dunkirk evacuation ends: British forces complete evacuation of 338,000 troops from Dunkirk in France. To rally the morale of the country, Winston Churchill delivers, only to the House of Commons, his famous "We shall fight on the beaches" speech.
1939 – The Holocaust: The MS St. Louis, a ship carrying 963 Jewish refugees, is denied permission to land in Florida, in the United States, after already being turned away from Cuba. Forced to return to Europe, more than 200 of its passengers later die in Nazi concentration camps.
1919 – Women's rights: The U.S. Congress approves the 19th Amendment to the United States Constitution, which guarantees suffrage to women, and sends it to the U.S. states for ratification.
1917 – The first Pulitzer Prizes are awarded: Laura E. Richards, Maude H. Elliott, and Florence Hall receive the first Pulitzer for biography (for Julia Ward Howe). Jean Jules Jusserand receives the first Pulitzer for history for his work With Americans of Past and Present Days. Herbert B. Swope receives the first Pulitzer for journalism for his work for the New York World.
1912 – Massachusetts becomes the first state of the United States to set a minimum wage.
1896 – Henry Ford completes the Ford Quadricycle, his first gasoline-powered automobile, and gives it a successful test run.
1876 – An express train called the Transcontinental Express arrives in San Francisco, via the First Transcontinental Railroad only 83 hours and 39 minutes after leaving New York City.
1862 – American Civil War: Confederate troops evacuate Fort Pillow on the Mississippi River, leaving the way clear for Union troops to take Memphis, Tennessee.
1825 – General Lafayette, a French officer in the American Revolutionary War, speaks at what would become Lafayette Square, Buffalo, during his visit to the United States.
1784 – Élisabeth Thible becomes the first woman to fly in an untethered hot air balloon. Her flight covers four kilometres in 45 minutes, and reached 1,500 metres altitude (estimated).