Dale Martin, professor of early Christianity at Yale, said in an e-mail: "An alternative theory (which I believe is much less likely) has suggested that the date of Christmas was set on Dec. 25 because it was supposed that Jesus' conception was the same date as his crucifixion. Since his death and also conception was supposed to have happened on March 25 (also speculation), then his birth would have been Dec. 25. I think this is much less likely as an explanation of the origin of the date."