August 23 – Ukraine celebrates the Day of the National Flag.
A bit of history:
1848 – a yellow and blue banner was adopted by the Main Ruthenian Council in Lemberg (Lviv, Western Ukraine), the capital of the then Kingdom of Galicia and Lodomeria, and flew over the city's magistrate for the first time. The flag was indeed yellow and blue, it was later changed upside down to blue and yellow to be more appealing to the common person.
March 25, 1917 – the blue-yellow flag was flown in Petrograd during a 20-thousand people mass demonstration for the first time in the Russian Empire. On April 1, 1917 a 100-thousand people demonstration carried over 320 national flags in Kyv.
March 10, 1919 – the first flag of the Ukrainian Soviet Socialist Republic (blue and yellow based on the red flag) was adopted to serve as the symbol of state of the Soviet Ukraine.
1949 – the flag of the Soviet Ukraine was changed once again: a red (top, 2/3) and a azure (bottom, 1/3) stripes with the golden star, hammer and sickle in the top left corner.
August 23, 1991 – a group of MPs brought a blue and yellow flag to the session hall of Ukraine’s parliament. That very flag is still being stored in the museum of the Verkhovna Rada as a relics.
January 28, 1992 – Ukraine’s Verkhovna Rada adopts the Law on National Flag approving it as a state one. The common interpretation of blue and yellow is "blue sky above yellow field of wheat".
2009 – President Victor Yushchenko founded an annual flag-raising ceremony on August 23.