Actually the most logical parallel would've been to have set the birth of the Carpenter to the pagan celebration of the birth of the Dying God (e.g. John Barleycorn?): in some traditions called Litha and usually set at February 1 (or thereabouts, midway between the Solstice and the Vernal Equinox).

But the political gain of making the BIG pagan holy day be the big Xian one made more sense finally.

Unless I'm mistaken, Biblical scholars claim that the historical Jesus was probably born in March or April? Assuming the description in Matthew is historical?

BB,
NightWing