The Origins of the Liturgical Year

Thomas Talley was a specialist liturgical historian, and this study directly sets out and weighs two competing scholarly explanations for why December twenty fifth became the date of Christmas, the calculation hypothesis, working from an ancient method of dating a holy figure's death and conception together, alongside the older history of religions hypothesis pointing to a pre-existing pagan solar festival, rather than asserting one explanation as settled. That direct, evidence weighing treatment of a genuinely disputed question is the study's real evidentiary basis. Use it for established scholarly facts about the two competing explanations for the origin of the December twenty fifth date and the evidence for each; it does not itself declare a single settled answer, so a claim asserting one explanation as proven should be checked against this source's own presentation of both.