JAMES TABOR has Some Thoughts on "Silent Night" at the Bible and Interpretation website. In it he discusses the possible birthdates (year and day) and paternity of Jesus, although he notes quite correctly that the any fine-tuned discussion of the date is based on evidence "which most historians would place wholly in the realm of the theological." I suspect the December 25th date really caught on because it helped keep Europeans from killing themselves from SAD in mid-winter.