20 September 1864

The United States military ended its "don't ask, don't tell" policy, consequently allowing gay and lesbian people to serve openly.

An explosive-laden truck detonated in front of the Marriott hotel in Islamabad, Pakistan, killing 54 people and injuring 266 others.

Hurricane Erika, the strongest and longest-lasting hurricane of the 1997 Atlantic hurricane season, dissipated after causing flooding and power outages throughout Puerto Rico.

British prime minister Margaret Thatcher (pictured) gave a landmark speech at the Belfry of Bruges, Belgium, against federalism in the European Economic Community.

The Cosby Show, which became one of three U.S. television shows to have the highest ratings five years in a row, premiered with its pilot episode.

A series of celestial phenomena of disputed nature was observed in the western Soviet Union, Finland and Denmark.

Billie Jean King defeated Bobby Riggs in straight sets at the Astrodome in Houston, Texas, in an internationally televised tennis match dubbed the "Battle of the Sexes".

Hurricane Irene (satellite image pictured) moved into the Pacific Ocean from the Atlantic, making it the first actively tracked tropical cyclone to do so.

L. Ron Hubbard, the founder of Scientology, announced the story of Xenu in a taped lecture sent to all Scientologists.

Second World War: Allied forces captured San Marino from the German Army.

World War II: Australian troops led by Gordon Grimsley King defeated Imperial Japanese forces at the Battle of Kaiapit in New Guinea.

Irish War of Independence: British auxiliary police officers known as Black and Tans went on a rampage in Balbriggan, burning more than fifty homes and businesses and killing two people.

The Bersaglieri entered Rome through the Porta Pia, ending the temporal power of the Pope and completing the unification of Italy.

The French Army achieved its first major victory of the War of the First Coalition at the Battle of Valmy.

The first of a series of treaties comprising the Peace of Ryswick was signed between France and the Grand Alliance, ending the Nine Years' War.

First English Civil War: The First Battle of Newbury was fought in Berkshire; Parliamentarian forces were allowed to pass Royalist troops to retreat the next morning.

A tsunami caused by the Meiō earthquake washed away the building housing the statue of the Great Buddha (pictured) at Kōtoku-in in Kamakura, Japan; the statue has since stood in the open air.

The second of two major uprisings by the Old Prussians, a Baltic tribe, began against the Teutonic Knights.

Harald III of Norway and his English ally Tostig Godwinson defeated the northern earls Edwin and Morcar at the Battle of Fulford near York.

Roughly four million people, mostly students, demonstrate across the world to address climate change. Sixteen-year-old Greta Thunberg from Sweden leads the demonstration in New York City.

At least 161 people die after a ferry capsizes close to the pier on Ukara Island in Lake Victoria, Tanzania.

Hurricane Maria makes landfall in Puerto Rico as a powerful Category 4 hurricane, resulting in 2,975 deaths, US$90 billion in damage, and a major humanitarian crisis.

The United States military ends its "don't ask, don't tell" policy, allowing gay men and women to serve openly for the first time.

A dump truck full of explosives detonates in front of the Marriott hotel in Islamabad, Pakistan, killing 54 people and injuring 266 others.