It is known as the Munich agreement or Munich betrayal.
Munich Agreement
"We are meeting on September 23rd" is the correct way to say it. The preposition "on" is used to indicate a specific date.
At the Munich meeting in 1938 of Neville Chamberlain and Adolf Hitler.
The Munich conference was a meeting of four European countries (Italy, France, Great Britain and Germany). The agreement allowed Germany to annex Czechoslovakia's Sudetenland. Czechoslovakia was not present at this conference, and it should be noted that this land contained key heavy industries, as well as 3 million Germans.
Sir Neville Chamberlain, after returning from the Munich Summit Meeting held with Adolf Hitler in 1938. He believed that he had secured Hitler's promise not to invad any more European nations after Germany annexed Austria and Czechoslovakia, but was forced to declare war on Germany on 3rd September the following year after Hitler invaded Poland.
Vienna
Congress of Vienna was a meeting of ambassadors of European states chaired by Austrian statesman Wenzel von Metternich. It was held in Vienna from September, 1814 to June, 1815.
Annapolis convention
In attendance during that meeting were the leaders of France Italy and the Great Britain
importation of European diseases.
Berlin Conference
potsdam conference