Christmas or Christmas Day is a holiday observed mostly on December 25 to commemorate the birth of Jesus. The earliest evidence of celebration of Jesus' birth comes from Clement of Alexandria, who describes Egyptian Christians as celebrating it on May 20, although other early sources have Christians celebrating the event in march, April, or January. According to Epiphaneus, Christians in the East had largely settled on January 6 by the fourth century. The wide-spread affiliation of Christmas with the Roman festival of Sol Invictus is disputable: there is no evidence that the feast of Sol Invictus was affixed by Aurelian to December 25. The celebration of Sol Invictus feast on December 25 is not mentioned until the calendar of 354 and, subsequently, in 362 by Julian the Apostate in his Oration to King Helios.[50] However, there is no month of the year to which respectable authorities have not assigned Jesus' birth