Official holidays

1 Jan: New Year’s Day (Yılbaşı)
23 Apr: National Sovereignty and Children’s Day (Ulusal Egemenlik ve Çocuk Bayramı) — anniversary of the establishment of the Turkish Grand National Assembly
1 May: Labour and Solidarity Day (Emek ve Dayanışma Günü, also unofficially known as İşçi Bayramı, i.e. Worker’s Day) was long banned as a holiday for almost 40 years and only restarted as a national holiday in 2009 because in years past it usually degenerated into violence. The wary traveller would be advised to not get caught in the middle of a May Day parade or gathering.
19 May: Atatürk Commemoration and Youth & Sports Holiday (Atatürk’ü Anma Gençlik ve Spor Bayramı) — the arrival of Atatürk in Samsun, and the beginning of the War of Independence
30 Aug: Victory Day (Zafer Bayramı) — Celebration of the end of the war for Turkish Independence over invasion forces. A big Armed Forces day and display of military might by huge military parades.
29 Oct: Republic Day (Cumhuriyet Bayramı or Ekim Yirmidokuz) is anniversary of the declaration of Turkish Republic. If it falls on a Thursday for example, Friday and the weekend should be considered in your travel plans. October 29 is the official end of the tourist season in many resorts in Mediterranean Turkey and usually there is a huge celebration at the town squares.
10 Nov, 09:05 — Traffic usually stops and sirens blare for two minutes starting at 09:05, the time when Atatürk, founder of the Turkish Republic, died in Dolmabahçe Palace in Istanbul in 1938. That moment in time is officially observed throughout the country but businesses and official places are not closed for the day. However, do not be surprised if you are on the street, you hear a loud boom and all of a sudden people and traffic stop on the sidewalks and streets for a moment of silence in observance of this event.
Religious holidays are same as all muslim countries.