Jan 1: New Year's Day
Apr 23: National Sovereignty and Children's Day (anniversary of the establishment of Turkish Grand National Assembly in 1920)
May 1: Labour and Solidarity Day (since 2009)
Aug 30: Victory Day (victory over invading forces in 1922).
Oct 29: Republic Day (anniversary of the declaration of the Turkish Republic in 1923)
Ramazan Bayrami: Three-day festival when sweets are eaten to celebrate the end of the fast of Ramadan month. Also known as "Seker (sweets) Bayrami" since it's customary to offer candies to family members and friends that are visiting.
Kurban Bayrami: Four-day festival when sacrificial sheep or cow are slaughtered and their meat distributed to the poor.
The dates of these religious festivals change according to the Islamic calendar and thus occur 10-11 days (exact difference between Gregorian and Lunar calendars is 10 days and 21 hrs) earlier each year. According to this;
Ramazan Bayrami (or Seker Bayrami) in 2015 is celebrated on 17-18-19 July, in 2016 it will be on 5-6-7 July, in 2017 will be on 25-26-27 June, in 2018 will be on 15-16-17 June, in 2019 will be on 5-6-7 June, in 2020 will be on 24-25-26 May.
Kurban Bayrami (Sacrifice holiday) in 2015 is celebrated on 23-24-25-26 September, in 2016 will be on 12-13-14-15 September, in 2017 will be on 1-2-3-4 September, in 2018 will be on 21-22-23-24 August, in 2019 will be on 11-12-13-14 August, in 2020 will be on 31 July - 1-2-3 August.
This religious holiday was celebrated on 31 December 2006 - 1-2-3 January 2007 and on 20-21-22-23 December 2007. As you can notice, there were two Kurban Bayrami dates in 2007, it's not a mistake but it happens every 32 years. Same with Ramazan Bayrami but it happened in 2000 and won't happen again until 2032.
About Muslim festivals & celebrations
The Festivals of Eid-ul-Fitr and Eid-ul-Adha.
There are two great holidays in Islam, 'Idul-Fitr, which falls on the first day of Shawwal, the tenth month of the Islamic year, and 'Idul-Adha, which falls on the tenth day of Thul-Hijjah and coincides with the Yauman-Nahr, "Day of the Sacrifices" in the Hajj Pilgrimage.
Eid-ul-Fitr, Ramazan Bayrami or Seker Bayrami in Turkish (the "Festival of the Breaking of the Fast"), occurs as soon as the new moon is sighted at the end of the month of fasting, namely Ramadan. Therefore, it's also known as Ramadan holiday.
On this festival people, having previously distributed the alms which are called the Sadaqatu'l-Fitr, assemble in the vast assembly outside the city in the Igdah, and, being led by the imam, recite two rak'ahs of prayer. After prayers the imam ascends the mimbar, or pulpit, and delivers the khutbah, or oration.
The igdah is a large place especially set aside for the large congregations who will attend the special Eid prayer early in the morning and can be an open field or flat piece of ground. It is only used as such on festival days for congregational prayers, the proper place always being the mosque on other occasions.
On the first day of Shawwal, the tenth month, comes the Ramazan ki'Id, or Ramadan celebration, when every one who fasts before going to the place of prayer (igdah) should make the customary fast offering (roza ki fitrat), which consists in distributing among a few Faqirs (poor) some 5 lb. (2.5kg) of wheat or other grain, dates and fruit. For until a man has distributed these gifts or the equivalent in money, the Almighty will keep his fasting suspended between Heaven and Earth.
The Eid prayer is not only said at an unusual place but is also conducted without the usual azaan (ezan), the call to prayer. This practice of omitting the azaan was allegedly practiced by Muhammad himself and is founded on this hadith (hadis):
Jabir bin Abdullah said, "The Prophet went out on the Day of 'Id-ul-Fitr and offered the prayer before delivering the Khutba". Ata told me that during the early days of Ibn-Az-Zubair, Ibn Abbas had sent a message to him telling him that the Adhan for the 'Id Prayer was never pronounced (in the lifetime of Allah's Apostle) and the Khutba used to be delivered after the prayer.
The festival is intended to be a festive and joyous occasion. Special foods and delicacies are prepared for the day and are distributed to neighbors and friends. Despite its importance it is considered inferior to the Eid-ul-Adha (Kurban Bayrami) and is known as the "little feast".
Eid-ul-Adha, Kurban Bayrami in Turkish (the "Feast of Sacrifice") is the great festival of Islam. It is also known as Baqri-Eid (the "Cow Festival") because its most important feature is the sacrifice of an animal (cow, goat, sheep, or other appropriate beast) in commemoration of the ram sacrificed by Abraham in place of his son. In Muhammad's time a camel was usually the animal sacrificed. The command to perform sacrifices is given in Surah 22.36 and although no specific day is fixed in the Qur'an the sacrificing of animals was already practiced on the last day of the pilgrimage by the pre-Islamic Arabs and the institution was duly retained. A special prayer, similar to the Eid-ul-Fitr prayer, is also offered on this day before the animals are sacrificed.
Narrated Al-Bara: I heard the Prophet delivering a Khutba (hutbe) saying, "The first thing to be done on this day (the first day of 'Id-ul-Adha) is to pray; and after returning from the prayer we slaughter our sacrifices (in the name of Allah), and whoever does so, he acted according to our Sunna (traditions) " (Sahih al-Bukhari, Vol. 2, p. 37).
Every Muslim home is obliged to offer a sacrifice on this day. The meat may be eaten by the family but a distribution of a generous share to the poor should also be made. As the two Eids (bayrams) are festive occasions, it is unlawful to fast on these days. Fasting on Eid-ul-Adha (Kurban Bayrami) would, in fact, defeat the whole object of the festival for food is to be eaten on this day with a cheerful heart in remembrance of God's bounty and provision for mankind. Umar once said:
The Apostle of Allah (may peace be upon him) prohibited fasting on these two days. As regards Id al-Adha, you eat the meat of your sacrificial animals. As for Id al-Fitr, you break (i.e. end) your fast. (Sunan Abu Dawud, Vol. 2, p. 663).
The name commonly given to the Eid sacrifice, qurbani (kurban), seems to have similar origins to the Jewish "Corban", meaning something set apart for God (Mark 7.11), and is probably derived from the Jewish word. Both Eids (bayrams) can last for two or three days but the prescribed rituals and prayers must be performed on the first day of each festival.
The Three Special Nights in the Islamic Year
Islam has three holy nights each year, the most important being Laylatul-Qadr (the "Night of Power") which is traditionally believed to be the 27th night of Ramadan. It is the night on which the Qur'an was allegedly brought down to the first heaven before being revealed to Muhammad and it is also the night on which special blessings are believed to be sent down on true worshippers from heaven:
We have indeed revealed this (Message) in the Night of Power: And what will explain to thee what the Night of Power is? The Night of Power is better than a thousand Months. Therein come down the angels and the Spirit by God's permission on every errand: Peace! ... This until the rise of Morn! Surah 97.1-5.
I had discovered the night of Qadr, but I have been made to forget. I think that I saw that I was performing sajdah on the morning of the Night of Qadr in mud and water. Seek it, therefore, in the last ten days at odd nights. (Muwatta Imam Malik, p. 128).
Other traditions say it falls on one of the last seven nights of the month. The night is also called laylatim - mubaarakah in Surah 44.3 - "a blessed night". This is one night of the year when every Muslim will seek to attend the evening prayer and the usual tarawih prayer of Ramadan.
The second great holy night of Islam is Laylatul-Bara'ah, the "Night of Record", which falls on the fifteenth night of Shabaan, the month before Ramadan. Once again every effort will be made to attend the mosque.
On this night, Muhammad said, God registers annually all the actions of mankind which they are to perform during the year, and that all the children of men, who are to be born and to die in the year, are recorded. Muhammad enjoined his followers to keep awake the whole night, to repeat one hundred rikat prayers, and to fast the next day. (Hughes, Notes on Muhammadanism, p. 116).
The night is also commonly known as Shabi-Baraat and it is said that there is a tree in heaven which sheds a number of leaves on this night, each one containing the name of someone destined to die in the coming year. The mercy of Allah, nevertheless, also descends on this night and sinners who repent are likely to obtain forgiveness in it. There appears to be a possibility that the night's significance may have Jewish origins.
In Jewish legend the world was created on New Year's day. No cosmological significance attaches to the First of Muharram, the official opening of the Muslim year. But the night of the Fifteenth of Sha'ban, lailat al-bara'a (behind which hitherto unexplained term the Hebrew beria, "creation", may be concealed) has preserved associations characteristic of a New Year's festival. (Von Grunebaum, Muhammadan Festivals, p. 53).
The third holy night is Laylatul-Mi'raj (Mirac), the "Night of Ascension", commemorating Muhammad's ascent to heaven. It is traditionally celebrated on the night preceding the 27th of Rajab, when the mosques and the minarets are lighted and there is much devotional reading of popular accounts of the Mi'raj.
The Other Minor Holy Days in the Islamic Year
There are really only two other days in the Muslim year that are regarded as especially important. One is the tenth of Muharram, the first month of the Islamic year. During Muhammad's life this day became a day of fasting in imitation of the Jewish fast of Ashura (cf. Exodus 12. 1-7). This practice was soon abandoned, however, and Muhammad is reported as saying that fasting on this day is not obligatory. After the massacre of Muhammad's grandson Husain (Hüseyin) and his band of followers at Karbala on this same day many years later, the whole of the first ten days of Muharram became a time of mourning for Shi'ite Muslims and today the day itself is observed in both Sunni and Shi'ite Islam as a remembrance of the tragedy at Karbala.
The other holy day is Maulidun-Nabi, the birthday of Muhammad, which falls on the 12th of Rabi-ul-Awwal. This festival of great feasting and many peculiar practices of un-Islamic origin is often frowned upon by the more orthodox Muslims and took some time to become widely observed.
The feast of the birth of the Prophet (milad, maulud in the Maghrib) is celebrated throughout the whole Muslim world on the 10th of rabi I; it seems to date only from the 10th century and to have become official only in the 12th.
One of the intellectual ancestors of Wahhabism, Ibn Taimiyya (d.1328), in a fatwa (legal opinion) tersely condemns the introduction of new festivals such as that celebrated "during one of the nights of the First Rabi, alleged to be the night of the birth of the Prophet". The participation of women was criticized with especial vigor by his contemporary, Ibn al-Hajj (d.1336), and it still gives occasional offence to the more strict-minded and orthodox. (Von Grunebaum, Muhammadan Festivals, p. 76).
Many Muslims openly concede that the practice of observing Muhammad's birthday is an innovation in Islam, something invariably disapproved of by conservative elements, but they excuse it as a "praiseworthy" innovation, a bid'atun-hasanah. It has also become customary to hold celebrations honoring various "saints" in Islam on this day as well, a custom considered even more reprehensible by orthodox Muslims. It seems likely that the Christian festival of Christmas gave rise to this equivalent in Islam. Ironically neither the actual date on which Jesus was born nor the birthday of Muhammad is known and the dates recorded are purely speculative. Even the Muslim world is not entirely unanimous in its determination of the date of the Maulidun-Nabi but it is now generally held to be the 12th of Rabi-ul-Awwal, coinciding conveniently with the date of Muhammad's death.
There are many other days in popular Islam that have become widely observed in the Muslim world, especially the Urs of any particular saint (usually his birthday when various unorthodox celebrations take place), but the two Eids (Bayrams) and the three holy nights are the great festivals of Islam and are the only ones universally observed by all Muslims without dispute as to the worthiness of the occasion.