Even in Christian circles, we often hear that Jesus' birth wasn't really in December. And even if the Messiah WAS born in December, then how in the world can we say that He was born on the 25th? Most Protestant and Catholic resources I've seen report that Christians co-opted the pagan solstice celebrations, placing Christmas on that date in order to "Christianize" the pagans.
Well, my dear online friend, Cheryl, investigated the actual date of Christmas. Raised in Christian family who didn't celebrate Christmas because they viewed it as a "pagan" holiday, she intended to "prove" that the Christ wasn't born in December at all, much less on the 25th. But what she discovered in ancient documents proved precisely the opposite.
Read her story here: http://www.geocities.com/cmeggers/Christmas.html
A blessed Christmastide to you!