Today's mainstream religious holidays are often clearly rooted in Pagan traditions.
For example, each year, the Christian celebration of Easter is based on the Pagan calendar: Easter is not a fixed-date holiday like Christmas is. Easter is the first Sunday after the first Full Moon after the Spring Equinox (Ostara). The cycles of the Moon determine if it will be an early or late Easter each year.
By studying the Pagan roots of modern-day seasonal celebrations, we can experience a richer understanding of why we celebrate what we do. Whether you are Christian, Jewish, Buddhist, Wiccan, or practice another religion, when you realize the significance of the celebrations and rituals, your spirituality can be enhanced in profound ways.
Holidays evolve steadily. The Christmas tree tradition began in the 7th century in Thuringia, Germany; Prince Albert--who was German--popularized the Christmas tree in England in the 19th century, around 1864.
Likewise, a hundred years from now, today's popular celebration of Christmas may be considered "old fashioned" or even "primitive." Some of these traditions will be discarded in favor of new ones, and some of the original significances may be lost.
It's important to remember the roots of our spiritual and seasonal celebrations, as far back as we can trace them. By following their evolution in practice and in spirituality, we can enhance our lives and our enjoyment of the holidays that cycle through the wheel of the year.