On the first day of the month of Mäskäräm, Ethiopians and Eritreans celebrate the beginning of the new year. Ethiopian new year is called Enkutatash in the Amharic language spoken in Ethiopia. It falls on September 11 (or September 12 during leap years) in the Gregorian calendar.
Teacher's Day is an important holiday celebrated in almost every country. However, its date varies from country to country. For example, Teachers Day in Argentina is celebrated on September 11 to commemorate Domingo Faustino Sarmiento, the seventh president of Argentina.
Day of Sobriety is an unofficial Russian holiday celebrated on September 11. It was first observed in 1911 or 1914 (according to different sources) and did not gain much popularity. Then the holiday was forgotten for a long time, until activists of Russian temperance movement decided to revive it in the 21st century.