|Holiday name||Holiday location||Holiday type|
|Restoration of Independence Day||East Timor||Public Holiday|
|National Day||Cameroon||Public Holiday|
|National Be a Millionaire Day||-||Unofficial (Lifestyle)|
|National Pick Strawberries Day||-||Unofficial (Activity & Action, Nature & Environment)|
|National Rescue Dog Day||-||Unofficial (Animals)|
|National Quiche Lorraine Day||-||Unofficial (Food & Drinks)|
|National Learn to Swim Day||-||Unofficial (Activity & Action)|
|Armed Forces Day||United States||Observance|
|World Autoimmune / Autoinflammatory Arthritis Day||-||International (Relationships & Family)|
|Day of Remembrance||Cambodia||Public Holiday|
Historical Events on May 20
- 1631: The Holy Roman Empire takes control of Magdeburg, Germany and massacres the majority of its residents during the 30 Years War.
- 1645: The Yangzhou Massacre occurs over a ten day period as over eight hundred thousand people are killed in Yangzhou city.
- 1802: The abolition of slavery is abolished as Napoleon Bonbaparte once again allows the French colonies to use slave labor.
- 1861: North Carolina secedes from the United States.
- 1861: Kentucky proclaims itself to be neutral during the American Civil War.
- 1862: The Homestead Acts is singed by United States President Abraham Lincoln.
- 1864: The Battle of Ware Bottom Church begins between Union forces led by Benjamin Butler and Confederate forces led by P. G. T. Beauregard. The church would be destroyed during the battle as Confederate forces win.
- 1873: A patent for blue jeans with copper rivets is obtained by Jacob Davis and Levi Strauss.
- 1932: Aviator Amelia Earhart’s plane takes off from Newfoundland and begins the first nonstop solo flight across the Atlantic Ocean by a female pilot. The next day, she would land in Ireland.
- 1940: A new concentration camp opens at Auschwitz and the first prisoners arrive on this day.
- 1949: The Armed Forces Security Agency in the U.S begins on this day. It would later become the National Security Agency.
- 1956: The 1stS airborne H-Bomb is dropped over the Bikini Atoll in the Pacific Ocean during Operation Redwing.
- 1964: Arno Penzias and Robert Woodrow Wilson discover background radiation emanating from the Cosmos.
- 1969: The bloody battle called the Battle of Hamburger Hill comes to an end on this day.
Famous Birthdays on May 20
- American Colonel, pilot and actor, Jimmy Stewart is born in 1908.
- American author Gardner Fox is born in 1911.
- American actress Edith Fellows is born in 1923.
- English singer-songwriter Joe Cocker is born in 1944.
- American singer-songwriter and actress, Cher is born in 1946.
- American Colonel, astronaut and engineer, Thomas Akers is born in 1951.