There are reasons why we celebrate Christmas on the 25th of December and it has nothing to do with appropriating the holidays of previous pagan festivals. The earliest Christmas celebrations known were around 200 A.D. This was prior to the point at which Christian traditions used existing festivals to make it easier for new converts and blending with the society at hand. Close to that time Christians in Egypt celebrated it in the spring, but by 300 AD, many observed it in December. So, what happened during that time?
The early church was more focused on the Death and Resurrection of Christ as opposed to His birth. Traditionally, a martyr’s death was used for the date of their conception. For Christ, the date of His crucifixion was believed to be the 14th of Nissan, or March 25th, per Tertullian of Carthage as he calculated around 200AD. So, 9 months from March 25th would be December 25th. This meshes with the Gospel of Luke and calculations based on the angel Gabriel’s announcement.
I for one was never really concerned with the date, but observing and thanking for the ultimate display of "if you want something done right, you need to do it yourself" is important.