DJIA (19 July 1987 through 19 January 1988).
FTSE 100 Index (19 July 1987 through 19 January 1988).
In financial markets, Black Monday refers to Monday, October 19, 1987, when stock markets around the world crashed, shedding a huge value in a very short period. The crash began on October 19 in Hong Kong, spread west to Europe, and hit the United States only after Hong Kong and other markets had already declined by a significant margin.
Another common theory states that the crash was a return to normalcy. Either way, program trading ended up taking the majority of the blame in the public eye for the 1987 crash is also referred to as Black Tuesday because of the timezone difference.)
The Black Monday decline was the largest one-day percentage decline in stock market history. Other large declines have occurred after periods of market closure, such as on Monday, September 17, 2001, the first day that the market was open following the September 11, 2001 attacks. (Saturday, December 12, 1914, is sometimes erroneously cited[3][4] as the largest one-day percentage decline of the DJIA.
