Seasonal rituals are as deeply embedded in most human cultures as music, dance and food. In agricultural societies, these were/are mostly tied to the major cultivation-centric events of the year. Commonly, you see rites intended to enhance luck or favor from the gods during planting season early in the year and celebrations of grace and bounty in the harvest season. The human brain has evolved to be exceptional at pattern-recognition (it’s supposedly what allowed us to dominate the planet) - what better patterns for us to celebrate than the most reliable, global patterns of all?
It’s easy to think of ceremony and ritual as being activities that belong to the divine, to faith, celebrations that exist on a societal level.