It is Life Day, a holiday that is celebrated on Chewbacca's home planet Kashyyyk. Chewie and Han Solo are trying to get to the planet where Chewie's family is waiting for him, but the Empire is out searching for the Rebels, giving everyone a hard time.
Along with being the start of spring on the Chinese calendar, Chinese New Year is about symbolically doing away with the old of the previous year and ushering in health, good fortune, prosperity, and happiness is the new year.
The traditional Chinese calendar is a lunisolar calendar which reckons years, months and days according to astronomical phenomena. It is used for traditional activities in China and overseas Chinese communities.