Rosh Hashannah is associated with the "Birthday of the World." It is supposed to coincide with the day on which G-d created Adam. Rosh Hashannah occurs in the fall, never close to March 25.
BTW, my non-Christian understanding is that the early Christians chose the date to coincide with the Roman Saturnalia so that their celebration would not be particularly conspicuous.
ML/NJ
The point of the article is that there are plenty explanation for the date of December 25 that are intrinsic to the Christian worldview, and not a result of a pagan influence.