The two biggest events in the postwar history of currency exchange markets are the Nixon shock of August 1971 and the Plaza Accord of September 1985.
In the first case, then U.S. President Richard Nixon terminated the convertibility of the dollar to gold. An attempt by an international conference of finance ministers in December that year to rebuild the system by devaluating the dollar ended in failure, leading to the collapse of the Breton-Woods system, which had supported the currency exchange regime since the end of World War II.
The Plaza Accord of 1985 then sent the dollar into a decline that would last for the next 10 years, defying efforts by monetary authorities to stabilize exchange rates in the Louvre Accord of 1987. The dollar, which stood at around 240 yen just before the Plaza Accord, was being traded below 90 yen in April 1995.