Festivals have become a part of our life, and we celebrate them: Sometimes even without knowing the exact background of them. As an example let us take Christmas, but that will follow later.
Festivals in general are special occasions for the people, they celebrate something special. They can have various reasons why they exist, but they all need one, even if it was just an Emperor who made something up. As such they can be based off the movement of the sun or rather the calendar, like Samhain and Beltane, or the cultural heritage like the National Day or based on special occasions of a person’s life, like the birthday.
The idea is to create some kind of outlet, which differs from the usual days: The excitement created is also used to influence the people in the way they behave, as can seen with a lot of charity going on especially during festivals and also a different atmosphere. However, festivals often are based upon religious traditions.