Annual Holidays around the world share a common thread of meaning regardless of culture and religious affiliation. There seems to be some deep psychological significance to the energy at the time of the year, regardless of climate and length of daylight.
I belief the common thread is the tension created by the elliptical orbit of the earth as it travels around the sun. Earth is pulled in this orbit between the electro-magnetic forces of the star we call our sun and the dense cluster of stars at the center of our galaxy. This group is often referred to as our "Great Central Sun."
At Winter Solstice, approximately December 21st, the earth is actually closest to our Sun. At Summer Solstice, Approximately June 21st, the Earth is pulled by the dense energy of the center of the Galaxy and the orbit is elongated to its furthest point away from the sun. The Equinox points are not only equal in daylight in the two Earth hemi-spheres; they are the same and at the mean point of the orbital distance between the Earth and the Sun.
These points mark major earth celebrations. The common threads are discussed in the article about each time of year. There are four more major periods for holiday celebrations and these coincide with the half-way time periods between the Equinox and Solstice points