Life Day was the fictional Wookiee holiday celebrated by the inhabitants of Kashyyyk, featured in The Star Wars Holiday Special. Unlike most aspects of the normally well-crafted Star Wars universe, Life Day is utterly expedient, inserted into the show to provide a very basic goal for the heroes, and lend a bit of topical relevance to the material, which would otherwise be completely inappropriate for a television holiday special.
Star Wars Holiday Special gives us some insight into the customs of Life Day. Chewbacca's wife prepares a feast, gifts are exchanged between acquaintances, candles are burned ritualistically, and Wookiees don red robes and join into groups to observe the day. Singing is involved.