Around 90 years ago the first president of the newly independent Turkey declared May 19th as Youth and Sports Day. In the present time this is the day that the Turks celebrate the man whom they refer to as the father of Turkey, Mustafa Kemal Atatürk who landed on May 19th 1919 to take command of the liberation effort.
During his time as president he declared May 19th as Youthand Sports Day, though I did not find why this was or how he thought it should be recognized. After his death people started to look to this day as when to remember Atatürk.
The day is celebrate in other parts of the world as well, a day to remember the Turkish heritage.