New Feather Festival

During the spring season, angels' thick winter feathers begin to fall out to make room for the thinner feathers that will keep them cool during the summer. 
Traditionally, the angelic calendar ended on the final day of spring and began with the start of summer, making the growth of new feathers a marker of the new year and hope to come. With the assimilation into the demonic kingdom, the calendar was changed to reflect a start in spring. However, the angels persisted in their festival and the tradition has continued to this day. Other species are welcome to attend the festivities as a cultural exchange.

Execution

The celebration lasts for two days and is split into specific parts depending on which day it is. 
On the first, all angels celebrating bring a single feather from their winter plumage to the center of their town, city, neighborhood, or other social gathering place in which they feel most comfortable. This is then placed into a large fire and sent into the sky to assist in heating the world during the coming summer months. This is also believed to bring good luck and fruitful harvest through the feathers' blessings. 
After this, street festivals, musical performances, and various traditional foods are eaten. 
The second day consists of celebrating the newly grown feathers. One of these is brought to the same place and bathed in water mixed with the ash from the previous day's bonfire to help the new wings grow strong until the winter shedding. 
Once all feathers have been washed, the water is poured over local crops or, in the case of large cities, onto the ground, so as to assist in natural or societal growth. The rest of the day proceeds much the same way as before, with street festivals and performances.