Much like a normal party, occur once a year. Colonist will gather around the sarcophagus or grave of their loved one (either bonded animal, family member, friends, etc.) to celebrate. They will offering food, gold, silver, jade , food or drug in a small amount to the death which can be reclaim afterward. They gain mood boost like normal party afterward if they are attend and not interrupt.
I'm quarter Chinese and our family have this ceremony every year around the beginning of April FYI.
https://donnagore.com/2015/01/29/remembering-the-anniversary-of-a-loved-ones-death/
Thank you for reading
:)