28th October each year (throughout Greece) - This event is held each year to commemorate the occasion when Greece said OXI (NO) to the invasion of Mussolini during the 2nd World War. There is a service at the main Cathedral church in the port followed by a parade by the children of Hydra.  After, there is a demonstration of traditional dancing and a general street party ensues.

In 1940 when most countries of Europe had surrendered, Hitler had the continent of Europe in his grip and the democracies were at their lowest point, Mussolini decided to take over Greece anticipating an easy victory based on his superior numbers and mechanized forces. He attacked Greece from Albania.
The Greeks stood up and said "OXI!!!" (No, you shall not pass) and fought fiercely, hurling back the stunned and bleeding aggressors. Mussolini's divisions were soon back in Albania and for six months were fighting to maintain a hold on the seacoast, desperately calling for help.

When Germany entered the war against Greece with the most powerful army in Europe, the Greeks continued to fight both of these great empires, although reason must have told them that their position was hopeless. Alongside their British comrades they continued to resist stubbornly on the island of Crete.

Greece had fallen, but it had cost Hitler thousands of his finest youth and delayed his attack against Russia by two months. German troops ran into the dreadful Russian winter and the Russians imposed such appalling losses that it contributed to the ultimate defeat of Germany. The occupation, Great Famine, resistance and subsequent liberation of Greece followed, and then came the "December Movement" in which Greeks fought brother Greeks.

Greece, with the help of England first and, later, of the United States, remained in the Western Alliance.