|Holiday name||Holiday location||Holiday type|
|Saint Ursula's Day||British Virgin Islands||Public Holiday|
|Overseas Chinese Day||Taiwan||Observance|
|World War II Victims Remembrance Day||Serbia||Observance|
|President Ndadaye's Day||Burundi||Public Holiday|
|Count your Buttons Day||-||Unofficial (Lifestyle)|
|Army Day||Honduras||National Holiday|
|Apple Day||-||Unofficial (Food & Drinks)|
|National Pumpkin Cheesecake Day||-||Unofficial (Food & Drinks)|
|National Reptile Awareness Day||-||Unofficial (Animals)|
|National Mammography Day||-||Unofficial (Awareness & Cause, Health & Body)|
|Hawke's Bay Anniversary Day||New Zealand||Local Holiday|
|International Day Of The Nacho||-||Unofficial (Food & Drinks)|
Historical Events on October 21
- 1797: The U.S Navy Frigate, the USS Constitution, is launched from Boston Harbor.
- 1805: French and Spanish forces under Admiral Villeneuve is defeated by British naval forces led by Vice Admiral Lord Nelson.
- 1861: Confederate forces defeat Colonel Edward Baker and his Union forces at the Battle of Ball’s Ball during the American Civil War.
- 1867: The Medicine Lodge Treaty is signed and requires Native America Plains tribes to relocate to a reservation in Western Oklahoma.
- 1879: An application for a patent for the incandescent light bulb is put into the U.S. Patent Office by Thomas Edison.
- 1888: The Swiss Social Democratic Party is founded.
- 1944: A Japanese fighter plane attacks the HMAS Australia located off of Leyte Island during the beginning of the Battle of Leyte Gulf.
- 1944: German civilians are killed by Soviet forces during the Nemmersdorf Massacre.
- 1944: During the Battle of Aachen, the city falls after 3-weeks of assault by Allied forces. This makes Aachen the first German city to fall to the Allies.
Famous Birthdays on October 21
- English poet and philosopher, Samuel Taylor Coleridge is born in 1772
- Italian baritone Filippo Colini is born in 1811.
- Swedish scientist, dynamite inventor and founder of the Nobel Prize, Alfred Nobel is born in 1833.
- American baseball player and coach, Whitey Ford is born in 1928.
- American basketball player and coach, Vern Mikkelsen is born in 1928.
- English author and poet Maureen Duffy is born in 1933.
- Canadian ice hockey player Carl Brewer is born in 1938.
- American actress Rhoda Germignani is born in 1940.
- American judge and TV personality, Judith Sheindlin is born in 1942.
- American economist and Nobel Prize laureate Christopher A. Sims is born in 1942.
- American singer-songwriter Matthew Friedberger is born in 1972.
- American football player Orlando Thomas is born in 1972.
- American pianist and composer Charlie Lowell is born in 1973.