<P> Although the month and date of Jesus ' birth are unknown , by the early - to - mid fourth century the Western Christian Church had placed Christmas on December 25 , a date that was later adopted in the East . Today , most Christians celebrate on December 25 in the Gregorian calendar , which has been adopted almost universally in the civil calendars used in countries throughout the world . However , some Eastern Christian Churches celebrate Christmas on December 25 of the older Julian calendar , which currently corresponds to January 7 in the Gregorian calendar , the day after the Western Christian Church celebrates the Epiphany . This is not a disagreement over the date of Christmas as such , but rather a preference of which calendar should be used to determine the day that is December 25 . Moreover , for Christians , the belief that God came into the world in the form of man to atone for the sins of humanity , rather than the exact birth date , is considered to be the primary purpose in celebrating Christmas . </P>
when was christmas first celebrated as a holiday
early - to - mid fourth century