To begin with, Christianity itself contained astrological elements; too many traces of the Hellenistic and Oriental religions, too much philosophy and science, were intertwined at its very roots for it to be able to rid itself of them completely. Accordingly, not only did the mythological names of the days of the week survive in spite of a certain amount of protest and some timid attempts to substitute a Christian terminology, but we even see the Church of Rome herself, in the middle of the fourth century, officially fixing the twenty-fifth of December as the date of Christ's nativity- the same day which had marked the birth of the Sun in the pagan religions, since the yearly course of each new sun has its beginning then. Aurelian, in his day, had made the sun a god of the Empire. Later, the first Christian Emperor was to have himself represented in the likeness of the Sun God on a porphyry column in Constantinople.
from page 43, The Survival of the Pagan Gods