Our papers devoted to teach of these topics and our introductory book, Who Are the Netzarim? (WAN), provide indisputable documentation showing that even Christian historians have acknowledged that Christmas (the birthday of M*ithra the sun G*od), E*aster (spring festival for I*shtar, also known as A*shtoret), the change from Shabat to Sun (G*od-) day and the like weren't syncretized into Christianity until several centuries after the death of Ribi Yehoshua!!! (You can also corroborate this information in any good encyclopedia.)