In Ukraine the day of January, 22th is celebrated as Unity Day and the Day of the Union between Ukrainian People's Republic (Ukrainian abbreviation УНР) and Western Ukrainian People's Republic (Ukrainian abbreviation ЗУНР) in one state. Union's Act between two Ukrainian states was declared on January, 22th in 1919 on Sofiyska Square in Kyiv and proclaimed unity of all Ukrainian territories. Though this Ukrainian state lasted very short time, but its existence is an important page in Ukrainian history. United Ukrainian state was finally broken in 1921 when Russia got Eastern Ukraine and Poland got Western Ukrainian territories (Halychyna, Volyn' and Polissya) according to the Document of Riga's Peace, signed between Poland and soviet Russia. In that time Zakarpattya (Transcarpathia) was Hungarian territory and Romania had Bukovyna (Chernivetska region in Ukraine now). So big dream of Ukrainians to have their own state after the breakup of Austro-Hungarian Empire of 1918, that dream was also broken. The reasons were diverse. On the one side Russian Army was bigger than Ukrainian in the military operations in the Eastern Ukraine, on the another side Poland was helped with British and French Army in the war with Ukrainian Sichovi Striltsi in the Western Ukraine and finally Russia and Poland signed "peace".
But it won't be honestly when I shan't tell You about other reasons why Ukrainian territory was divided again in the XXth century. There were much differences in the views of how to rule of the country and what enemy is dangerouser (Russia or Poland) between the chieves of that Ukrainian state. That's why Ukrainian Unity Day is a few symbolic holiday too and today reminds citizens of Ukraine that citizens' unity exactly is that principal base against any enemy.

http://www.youtube.com/watch?v=uD2utqoaH38

Celebration of Union Day on January 22th, 2011 in Kyiv. There is a tradition to take the arms each other in the streets of all Ukrainian cities and to create people's chain as a symbol of the nation's unity.