World Parkinson's Day, also referred to as World Parkinson's Disease Day or World Parkinson's Awareness Day, is an annual global awareness day aimed at promoting a better understanding of this health condition. It is observed on April 11.
International Louie Louie Day is an annual holiday dedicated to Richard Berry and his famous rhythm and blues song “Louie Louie”. It is celebrated on April 11 (Richard Berry's birthday).
In some countries, April 11 is observed as Day of Nazi Concentration Camps Prisoners Liberation. It marks the anniversary of liberation of Buchenwald concentration camp in 1945.