Touchstone Magazine has a great article in its archives about how we calculate the date of Christmas. Occasionally, you will hear that the dates for Christ’s birth and death are completely artificial and based on pagan festivals. To read the truth, read William Tighe’s article. A snippet:
December 25th as the date of the Christ’s birth appears to owe nothing whatsoever to pagan influences upon the practice of the Church during or after Constantine’s time. It is wholly unlikely to have been the actual date of Christ’s birth, but it arose entirely from the efforts of early Latin Christians to determine the historical date of Christ’s death.