|Holiday name||Holiday location||Holiday type|
|National Day||Chile||National Holiday|
|Rice Krispie Treat Day||-||Unofficial (Food & Drinks)|
|National Cheeseburger Day||-||Unofficial (Food & Drinks)|
|Airforce Birthday||-||Unofficial (Appreciation & Honor)|
|National HIV/AIDS and Aging Awareness Day||-||Unofficial (Awareness & Cause, Health & Body)|
|Air Force Birthday||United States||Observance|
|Constitution Day and Citizenship Day observed||United States||Observance|
|Tzom Gedaliah||Israel||Observance, Hebrew|
|Respect for the Aged Day||Japan||National Holiday|
|Federal Fast Monday||Switzerland (Vaud)||Common Local Holiday|
|Ganesh Chaturthi||Mauritius||Hindu Holiday|
Historical Events on September 18
- 1180: Philip II was crowned King of France.
- 1454: During the Thirteenth Years War, the Teutonic army defeats the Polish army at the Battle of Chojnice.
- 1502: On his final voyage, Christopher Columbus lands at Honduras.
- 1618: The 12th Baktun begins in the Mesoamerican Long Count Calendar.
- 1739: Belgrade is ceded to the Ottoman Empire when the Treaty of Belgrade is signed.
- 1809: The Royal Opera House opens in the city of London.
- 1850: The Fugitive Slave Act of 1850 is passed by the United States Congress.
- 1851: The New York Daily Times is published for the first time; This newspaper would go on to become the New York Times.
- 1873: Jay Cooke & Company – a U.S. Based bank – declares bankruptcy. This leads to a series of bank failures and would eventually be dubbed the Panic of 1873.
- 1927: CBS goes on the air for the first time.
- 1934: The USSR joins the League of Nations.
- 1940: The SS City of Benares – a British liner – is sunk by torpedoes from a German U-48 submarine. Almost 80 child refugees are among the dead.
- 1943: Danish Jews are deported by Hitler during WWII.
- 1943: At Sobibor, Jews are massacred.
- 1947: The U.S Air Force becomes its own independent brand of the U.S Armed Forces.
- 1964: South Vietnam begins to become infiltrated by the North Vietnamese Army.
- 1973: East Germany and West Germany join the U.N.
- 1973: The Bahamas join the U.N.
- 1977: The first photographs of the Earth and Moon together are taken by Voyager I.
- 1982: Over six hundred Palestinians are killed by Christian militias in Lebanon.
Famous Birthdays on September 18
- Swedish-American actress Greta Garbo is born in 1905.
- French actor Maurice Maillot is born in 1906.
- Canadian ice hockey play Syd Howe is born in 1911.
- American actress June Foray is born in 1917.
- American actress and TV host Aisha Tyler is born in 1970.
- American cyclist Lance Armstrong is born in 1971.
- American actress Jada Pinkett Smith is born in 1971.
- American actor James Marsden is born in 1973.