Harmony Day is a Holiday first created by the Crystal Gems in the episode "Holly Jolly Harmony". It's their in-universe representation of Christmas, just as Hearth's Warming is to Equestria. It's celebrated four days after the "birth-iversary" of Lapis Lazuli (anniversary of her joining the Gems) and Stevonnie (her birthday).
Origin
The holidfay itself was first started during Connie II's first visit to Beach City. During her stay she questions the Crystal Gems if they ever really had a holiday off from all of their work, the only true holiday in Beach City prior to this being Halloween. Steven decided to make their own holiday in a spur-of-the-moment idea to celebrate.
Traditions
Throughout the episode, There is a number of traditional requirements that were brought forward by the Gems and Mane Six, and what Harmony Day's all about:
- Those celebrating have the option to wear "Fun Flower shirts", as it shows love and harmony amongst eachother.
- Steven Universe describes that Harmony Day is about having fun with your best friends and family, and that everyone should treat eachother friendly.
- Adopted from Hearth's Warming, a mistletoe is hung from a door frame, and when two people are standing underneath the Mistletoe they kiss. This is shown with Sapphire kissing Peridot, and then later Ruby.
- Near the end of the day, presents are exchanged and are opened on the same evening.