Maybe sth non-comie will replace it, one day..
November 11th can be considered such a day. It's after 1918, November 11th - the date of recreation of Poland after 123 years not being an independent country. And this holiday was forbidden to celebrate in the communist times.
Also May 3rd - for 1971, May 3rd - the date of introducing the first Polish constitution, which was the first (in the modern sense) constitution in Europe and the second in the world. Also forbidden in the communist times.
After the fall of communism it was decided that there is no more use in celebrating overtaking the power in Poland actually by Soviets, so it's not celebrated on a large scale any more. Even though the end of the war, of the German occupation, and becoming back an independent country (even though not truly independent - but it's difficult to mark a clear border between independence and lack of independence, some people say Poland is not independent now, and we were at least marked as a country on maps, not like before 1918) may be a reason to celebrate anyway.
Actually one could claim that there is no true independence of countries in the modern world (maybe except for North Korea, but their economic situation is in these conditions worse than bad), all of them are connected by a lot of economic relations and all of this is very complicated. But one country suddenly disappearing would cause a lot of problems for the other countries.