Islamic holidays are calculated according to the lunar calendar and vary from year to year. A major Islamic festival is the three-day holiday called " Seker Bayrami " ( Sugar Holiday ), which comes at the end of the month-long fast of Ramazan ( Ramadan ). A favorite treat at this time is rahat lokoum colorful gelatin cubes covered with powdered sugar, known in English as Turkish delight . A four-day Islamic holiday called " Kurban Bayrami " ( Sacrifice Holiday ) honors Abraham's willingness to sacrifice his only son, Isaac, at Allah's command. It also marks the season of pilgrimage to Makkah (Mecca). An animal is usually sacrificed on this day to symbolize Allah's allowing Abraham to sacrifice a ram instead of his son as a reward for his demonstration of obedience. Secular holidays in Turkey are calculated according to the Western calendar. Other official holidays include " New Year's Day " (1 January);" National Sovereignty Day " (23 April, coinciding with Children's Day), " Ataturk's Memorial Day " and " Youth Day " (19 May); " Victory Day " (30 August); and " Republic Day " (29 October). The day before Republic Day is also a holiday in some areas. August is when most people take their annual holiday. National Sovereignty Day commemorates the Grand National Assembly's inauguration on 23 April 1923. Since it coincides with Children's Day, 400 students are given the chance to take seats in the national government in the nation's capital for the day. Ataturk's Memorial Day and Youth Day commemorates the beginning of the national movement for independence in 1919, led by Mustafa Kemal Ataturk. On Victory Day, military parades are held, the world's oldest military band the Mehtar band plays, and fireworks are set off. Republic Day celebrates the anniversary of the founding of the republic in 1923.