Sorry Tommy for being late to the party.
Yes, Jesus was more likely born in spring or summer. Romans are very practical people and most likely would have organised the census (Joseph and Mary were in Bethlehem because of census requirements) in spring/summer when days are longer and warmer.
And yes, it is likely the Church chose the unknown-dated Christmas to be 25 Dec in order to Christianise a pagan festival. At that time, there was in Rome a week-long festival of Saturnalia to celebrate the winter solistice from 17-23 Dec. The festival was very popular among Romans and culminated on 23 Dec as the Birthday of the Unconquerable Sun, from which day the days gets longer - it got shorter and shorter but never got diminished and was reborn to get longer from that day onwards.
On the basis of 'if you can’t beat them, join ‘em’ basis, I guess, the Church in her wisdom chose not to fight a popular week-long revelry and chose instead to impart a Christian understanding to all those symbols. So Christmas was 25 Dec in Rome from at least early third century onwards.
It was easy for the ‘Unconquerable Sun’ to become the sacrificed saviour that death could not conquer. Saturnalia’s gift-giving morphed into Christian charity and gift-giving inspired by St Nicholas’ gifts to the three peasant girls.
The pagan laurel evergreen used to symbolise the undying Sun came to symbolise the saviour whom death could not conquer. The evergreen’s symbolism later found its way into the Advent wreath, which itself was a pre-Christian Germanic symbolism - the eternity of the circle became a symbol of the eternal Jesus without beginning and end, another way of saying alpha & omega I guess.
Also, New Year’s day in those days was 25 March, the spring equinox (it is very strange to us, as it will be 24 March 2015 and then the next day is 25 March 2016). Christian symbolism would mean that 25 March becomes the start of a new era and so it became the date when the saviour of the world was conceived - the Annunciation. And 9 months later the birth of the saviour takes place on 25 Dec.
[Sorry for the non-American dating method but sometimes the rest of the world would like to declare our independence from Americanism


]
In the end, it is an issue anyway?
No, as it just shows what Catholicism and Christianity is all about. Being a universal religion, it is adaptable to local practices and draws its heritage from the common inheritance of human society in all forms the way God created us. What is important is not so much whether the symbolism is Christian or pagan in origin but what what do we have in our mind today when we hold the symbol or perform the act in question.
I am an ethnic Chinese and in Asia, the Catholic Church has no issue with ethnic Chinese praying with joss-sticks like those Chinese do in Buddhist & Taoist temples. We just have to make sure that we do not pray to our ancestors but are praying for them and paying them our respects. The joss-stick is not religious in nature, but deemed by the Church to be cultural.
The Church calls this
inculturation and this is what makes me proud to be Catholic. Being Catholic means people coming together from different backgrounds, different languages, different cultures but bound in one faith. This is a lot more apparent to non-white Catholics who live outside the Europeanised world. Those Jehovah Witnesses and Evangelical Christians (and indeed fundamentalist Catholics) have only burnt their rich heritage when they insist on only a Christian history for everything they do.
One last thing - looking at the current commercialisation of Christmas, one priestly friend of mine remarked that** it does look like the pagans have reclaimed Christmas**. I think he does have something for us to think about.