I do not celebrate Christ's birth on December 25th. However, I do celebrate Christ's conception on that day.
I understand that the Pagan feast of Saturnalia is celebrated on the day of first full moon after the winter solstice. The full moon doesn't always occur on the 25th due to a lunar month being shorter than a solar month. When the Christian church began growing in the first few centuries and especially in the Dark Ages and Middle Ages and converts were being added in huge numbers, many of those converts were Pagans who celebrated Saturnalia. Because the dates of Christ's conception and the feast of Saturnalia are so close together (in fact the having a full moon on Christmas day happens periodically including this year), the Christian church in the past should have in fact outlawed any Pagan celebrations. They didn't. Instead the church embraced the practices of the Pagans because it made for much happier converts and much more revenue. The same happens in the Spring when the Pagan feast of Easter is celebrated instead of the Biblical feast of Passover.
I believe Jesus was born in the fall of the year, either September 28th or 29th which according to the Solar calendar and not the Jewish lunar calendar is the feast of Tabernacles. Tabernacles was an Israelite festival, a high Sabbath, appointed by God, that celebrated the coming of Passover. I believe Christ was born on the second holiest day of the year, Tabernacles. And He died on the holiest day of the year, Passover. Both festivals are high Sabbaths. I do not find any Biblical evidence as to why Christ's birth should or should not be celebrated. However, I do find evidence that the Feast of Tabernacles and Passover should be.
Where the dating goes wrong on Christ's birth is regarding the course of Abia, as mentioned in the Gospel of Luke. There were 24 priestly courses according to the Levitical priesthood. Abia was one of them. The course of Abia happened not once but twice in the run of a year, a very specific time when the Levitical priests performed their duties in the temple. If you choose the wrong date for the course, you will get the result of December 25th for Christ's birth. If you choose the other, you will get September 28th or 29th as the birthdate because the Israelite New Year was a solar year and not a lunar year. New Year's Day for an Israelite started at the Spring equinox when the sun was directly over the equator. And that occurs on either the 21st or 22nd day of March.
In my church, some members do celebrate Christmas Day. Other do not. Many others, like myself, celebrate Christmas Day in September. But we recognize December 25th as Christ's conception day and not his birthday. Some members like myself, do not have a Christmas tree or have Christmas dinner or give gifts. I consider it a day of reflection and have Communion and read the Word.
I actually believe Jesus celebrated his birthday as recorded in John's Gospel; John 7:37. The last and greatest day of the Feast of Tabernacles:
John 7:37 In the last day, that great day of the feast, Jesus stood and cried, saying, If any man thirst, let him come unto me, and drink.
The other very interesting thing about the Feast of Tabernacles is that it is the only feast day that the Bible records that is celebrated in the future:
Zechariah 14:16 And it shall come to pass, that every one that is left of all the nations which came against Jerusalem shall even go up from year to year to worship the King, the Lord of hosts, and to keep the feast of tabernacles.
Zechariah 14:17 And it shall be, that whoso will not come up of all the families of the earth unto Jerusalem to worship the King, the Lord of hosts, even upon them shall be no rain.
Zechariah 14:18 And if the family of Egypt go not up, and come not, that have no rain; there shall be the plague, wherewith the Lord will smite the heathen that come not up to keep the feast of tabernacles.
Zechariah 14:19 This shall be the punishment of Egypt, and the punishment of all nations that come not up to keep the feast of tabernacles.
I do know the real reason for the season; Christ's conception. However, I completely disagree with any form of Pagan worship and especially what the modern Western culture mindset has done to December 25th. Western culture has turned Christmas into a business.
If anyone wants to read up on the correct date, then they can check out the following links for the Course of Abia.
1/ Parallel Datings of the Time of our Lord
http://levendwater.org/companion/append179.html#times
2/ Dates of the Begetting of our Lord and His birth
http://levendwater.org/companion/append179.html#begetting
3/ The Course of Abia
http://levendwater.org/companion/append179.html#abia