That is why it is called so!!!)))Now, i have understood.Sorry for the fact that I didn't know it...In my opinion?this holiday is very useful for keeping  piece and unity of the peoples

Officially, National Unity Day commemorates the popular national resistance that led to Moscow’s liberation from occupying Polish-Lithuanian forces, marking the end of what later became known as Russia’s Time of Troubles. The idea behind the holiday is that people from a diverse group of ethnic and religious backgrounds banded together in a popular insurrection, which succeeded in ejecting foreign occupiers who had brought nothing but destruction and despair to Russia during their brief rule.

The date itself, Nov. 4, was chosen because it marks the first successful act of resistance to Polish-Lithuanian rule in 1612 ­ the seizure of Moscow’s Kitai-Gorod by Prince Dmitry Pozharsky and Kuzma Minin. Moscow’s actual liberation did not take place for several more days, and most historians attribute the first Romanov’s ascension to the throne in early 1613 as the official end of the Time of Troubles.

The holiday’s creation last year received enthusiastic support from the Russian Orthodox Church, which has long attributed the events of 1612 to one of Russia’s most famous icons ­ Our Lady of Kazan. Indeed, for more than three centuries the church has celebrated Nov. 4 as a day of veneration for the Kazan icon. According to one legend, the icon itself was discovered in Kazan in 1579 after a church fire, and was taken to Moscow in 1612 in belief that its protective powers would aide the popular insurrection mounted by Pozharsky.

By the way, the 7th of November  used to be a great  holiday too! 1917, Russian Revolution: In Petrograd, Russia, Bolshevik leaders Vladimir Lenin and Leon Trotsky lead revolutionaries in overthrowing the Provisional Government (As Russia was still using the Julian Calendar, subsequent period references show the date as October 25).

You know, recently I have come across the TV broadcast, where the journalists were asking people of different ages about this holiday. Among the ELDER generation, only FEW remember it! Of course, it goes without saying, that younger generations didn't even hear of the holiday.