Since Wicca is derived from ancient European agrarian societies, the Sabbats are closely tied to the seasons and the calendar.
Sabbats have been followed for many thousands of years by ancient cultures such as Nordics, Celtics, Greeks, Egyptians.
Vestalia is a weeklong celebration that honors the Goddess, Vesta of the Roman pantheon. She worked alongside the goddess Juno, and both of them guarded virginity and protected the sanctity of marriage.
Beltane is a festival that is celebrated every first day of May where the participants wear flowers in their hair, create maypoles and go into frenzied fire dancing at night. Can you picture trick or treating in spring? It's something like that..
The ritual is best just around Ostara, but with slight modifications you can perform at midsummer, Mabon and Yule as well.
Much of what we are doing during Christmas, has very little to do with the birth of Jesus and everything to do with the celebration of Yule and the change of the seasons.