Bayram is the Turkic word for a nationally-celebrated festival or holiday, applicable to both national (i.e. secular) and religious celebrations. In accordance with this dual applicability, the method with which one determines the yearly timing of Bayrams is different for national and religious holidays.
State holidays in Turkey have set dates under the nationally-used Gregorian Calendar, while the Islamic religious holidays are coordinated and publicly announced in advance by the Government's Presidency of Religious Affairs department according to the Lunar Calendar, and are subsequently accommodated into the national Gregorian Calendar, which results in the dates for religious holidays changing every year with a shift margin of approximately 11 days.

Large scale non-Turkish or non-Islamic traditions and celebrations may similarly be called Bayram, as illustrated by Halloween being referred to as "Cadılar Bayramı" (i.e. "Bayram of Witches"), Easter as "Paskalya Bayramı" (i.e. "Easter Bayram"), Christmas as "Noel Bayramı" (i.e. "Christmas Bayram"), Passover as "Hamursuz Bayramı" ("No-dough{meaning 'yeast'} Bayram"), and Hanukkah as "Yeniden Adanma Bayramı" (i.e. "Renewal/Rededication Bayram"). However, not every special occasion or holiday is referred to as a Bayram, as illustrated by the case of World Health Day, or Liberation of Istanbul, among others.
Likely owing to the enduring Ottoman Turkish influence in the Balkans and parts of South-Eastern Europe, many non-Turkish peoples like Albanian Muslims, Gorani people, Pomaks and Bosniaks, as well as Muslims from the Northern Caucasus, Azerbaijan, Crimea and other Turkic peoples, have similarly adopted the use of the word "Bayram", using the term "Lesser Bairam" to refer to their own Eid al-Fitr celebrations; "Greater Bairam" refers to Eid al Adha.[1]
National festivals of Turkey
• New Years' Day ("Yılbaşı" or "Yılbaşı Bayramı")
• National Sovereignty and Children's Day ("Ulusal Egemenlik ve Çocuk Bayramı"), April 23 (1920)
• Workers' Day ("İşçi Bayramı"), May 1
• Commemoration of Atatürk, Youth and Sports Day ("Atatürk'ü Anma, Gençlik ve Spor Bayramı"), May 19 (1919)
• Victory Day ("Zafer Bayramı"), August 30 (1922)
• Republic Day ("Cumhuriyet Bayramı"), October 29 (1923)
Religious festivals of Turkey
• Eid al-Fitr ("Şeker Bayramı", i.e. "Bayram of Sweets", or, "Ramazan Bayramı", i.e. "Ramadan Bayram"), 1st of Shawwal
• Eid al-Adha ("Kurban Bayramı", i.e. "Sacrifice Bayram"), Dhu al-Hijjah 10-13
Folk festivals
• Kosaqan or Yılgayakh - A spring feast and festival Turkic and Altai folklore.
• Sayaqan or Yhyakh - A summer feast and festival Turkish folklore. So this is a blessing, fertility and abundance ceremony.
• Paktaqan - An autumn feast and festival Turkic and Altai folklore.
• Paynaqan - A winter and pine tree feast and festival like Christmas in Turkic and Altai folklore.
• Nardoqan - Nardoqan or Narduğan was a Sumerian and Turkic-Mongolian holiday, referred to the winter solstice.