https://en.wikipedia.org/wiki/Ohi_Day

Ohi Day or Oxi Day (Greek: Επέτειος του Όχι, Epéteios tou Óchi [eˈpetios tu ˈoçi]; "Anniversary of the No") is celebrated throughout Greece, Cyprus and the Greek communities around the world on 28 October each year. Ohi Day commemorates the rejection by Greek Prime Minister Ioannis Metaxas of the ultimatum made by Italian dictator Benito Mussolini on 28 October 1940, the Hellenic counterattack against the invading Italian forces at the mountains of Pindus during the Greco-Italian War, and the Greek Resistance during the Axis occupation.