„In short, we have no clear evidence that a festival dedicated to Sol Invictus was celebrated on December 25 prior to the Christian celebration of Christmas on that date. More importantly, we do not have any evidence that such a pre-existing festival presented the impetus for celebrating Jesus’s birth on this day. The popularity of this assertion and various sub-assertions around it (such as its institution by Aurelian) is not commensurate with its evidential basis.“

https://medium.com/christian-history-and-culture/why-is-christmas-on-december-25-7b7b6334fd84