The People’s Republic of China celebrates its National Day on 1 October every year – or rather, on and around 1 October. Since 1999 it’s been the focus of one of two “Golden Weeks”, annual holidays where all workers receive three days’ paid holiday and the weekends are arranged so that everyone gets seven consecutive days off. (The other one is Chinese New Year.)
The National Day celebrates the founding of the People’s Republic of China on 1 October 1949, after near-total victory in the Civil War that had been fought on and off since April 1927. The defeated Nationalists led by Chiang Kai-Shek retreated to Taiwan. (Arguably the Civil War is still continuing, since there was never any formal peace between the two sides and both sides tacitly agree not to acknowledge each other as an independent state.)
The major element of the celebrations is the parades through Beijing’s historic heart, in particular the display of military might by the People’s Liberation Army. There are also many firework displays, including in the two Special Administrative Regions of Hong Kong (since 1997) and Macau (since 2000).