August 21st is the 233rd day of the year (234th in leap years) in the Gregorian calendar. There are 132 days remaining until the end of the year.
1140 – Song dynasty general Yue Fei defeated an army led by Jin dynasty general Wuzhu at the Battle of Yancheng during the Jin–Song Wars.
1831 – Nat Turner led a slave revolt in Southampton County, Virginia, U.S., which was suppressed about 48 hours later.
1944 – World War II: A combined Canadian–Polish force captured the strategically important town of Falaise, France, in the final offensive of the Battle of Normandy.
1993 – NASA lost contact with its Mars Observer spacecraft, three days before orbital insertion.
2015 – Passengers subdued an attacker in a train heading from Amsterdam to Paris, resulting in four injuries, including the attacker himself.
Kim Cattrall turns 62
Carrie-Anne Moss turns 51
Usain Bolt turns 32
Hayden Panettiere turns 29
Bo Burnham turns 28