No one knows for sure when Jesus was born. Some biblical scholars suggest it may have been around the month of July, August or September. Most all agree it could not have been in December.
In the 4th century, the Roman Catholic Church chose December 25th as the day to celebrate the birth of Christ or "Christ Mass" (even though nowhere in the Bible does it state we should celebrate Christ's birth). At the time, Romans were celebrating the Roman winter festival Saturnalia, commemorating the dedication of the temple of the god Saturn, and Dies Natalis Solis Invicti, "the birthday of the Unconquered Sun". It is believed that the Church wanted to convert people without them having to give up their holidays. So, instead, these pagan holidays were incorporated into the Christian church under the guise of "Christ Mass".
Some people believe Saturnalia was the inspiration for the pagan festival of Yule, which celebrated the birth of the pagan Sun God, Mithras. Although not on the exact same days, Christmas customs are nearly identical to the customs of the people during these pagan winter holidays. For example, during Dies Natalis Solis Invicti "Mummers" were groups of costumed singers and dancers who traveled from house to house entertaining their neighbors. From this, the Christmas tradition of caroling was born. During the pagan festival of Yule, evergreen trees were worshipped. Mistletoe was considered a sacred plant, and the custom of kissing under the mistletoe was as a fertility ritual. Candles were lit to encourage Mithras, and the sun, to reappear next year, and hollyberries were thought to be a food of the gods. The word Yule actually means "wheel," a pagan symbol for the sun. In German paganism, Odin was a chief God with a long white beard. Children would place their boots, filled with carrots, straw or sugar, near the chimney for Odin's flying horse, Sleipnir. Odin would then reward those children for their kindness by replacing Sleipnir's food with gifts or candy. Sounds a lot like Santa Claus, but instead of boots, we now have Christmas stockings.
Today during Christmas celebrations, along with the pagan traditions of Santa Claus, caroling and mistletoe, some are found to still be worshipping the tree: "Oh, Christmas tree, Oh, Christmas tree, with all our hearts we love thee."
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It is possible to determine with the bible that Jesus was indeed born the 25 th of December. The Qumram texts show us that the priestly courses were continuously serving from Shabbat to Shabbat and scriptures say that there were 24 courses. The destruction of the temple was the nineth of Av 70 A.D. which was the 2 August. The ruling of Quirinus started in 6 BC and Herod the Great died on March 4 BC, so Jesus must have been born shy 2 years prior for he decreed the death of the boys of 2 years old or under. Therefore what you do is calculate the course of Abijah, whish is the eight, going backwards from 70 A.D. and you come to the conception of John the baptist, then 5 months and one day to the conception of Jesus and from there 9 months to the birth of Christ, the shabbath 25th of December 6 BCE at the solstice at 9:21 PM. His conception was in the month of March of the same year at Pesac. The Prophet Malachi calls him appropriately The Risen Sun. Julius Africanus and other anti Nicene writers acknowledge this date or a close date. There is evidence of christmas celebrations up to 150 A.D. There are also solstices that are pretty warm in the Bethlehem area, allowing the shepards to vigil their flocks as it is said by the evangelist
Now, most of the Cristian comunity worldwide, with just a few exceptions acknowledges Christmas as a joyful occasion and one starts to see preparations for the season as early as the ends of September and the beginning of October.
Saying that the celebration of his birth was not a mandate is a half truth, for the very night of his birth the angels of God celebrated along with the Shepard.
Saying also that some traditions are add ons from the old pagan customs is true, however, vilifying everything that has pagan origin is a big mistake. For we could not use ties, wedding rings, pants and other common things of our daily life.
Witches are known by their use of medicinal herbs, but that does not mean we should not drink a chamomile tea in good conscience.
Everyone agrees that the 3 wisemen were not israelites, and many would call them pagan, however they brought presentes to the Lord and they were accepted by Mary and Joseph!
Actually, the Wisemen were zoroastrian priest which is a monotheist religion that believes in only one God Aura Mazda, and that were waiting the coming of the King of Kings that prophet Zaratustra foresaw.
Stars are also used in magic and divination, however the prophet Balaam foresaw Jesus by inspiration and said: "...;there shall come a Star out of Jacob, and a Prince shall rise out of Israel,..." Numbers 24:17
So, there is the star!
And how many have slandered this wonderful wisemen, saying that they were astrologers, when zoroastrians repell astrology up to the present time!
Astrologers try to predict the future from the stars, this men just saw the star of the Prince and followed it! Actually the scriptures call stars to the angels of heaven. Perhaps the star was an angel that told them about the birth. This would explain how a star could guide them to a fixed point on earth. One just cannot follow an actual star and get anywhere.
So, Christmas has a lot to do with Christ and is genuine christian tradition.
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As stated in above Answers, December 25th is a pagan festival and has nothing to do with Christmas. (Indeed, Satan knows Scripture better than anyone and has had plenty of time to counterfeit ALL Christian festivals and Holy Days/Holidays). It is known that traditionally in the Middle East a person's age was reckoned from their time of conception and not their birth, which would make Jesus born late September - possibly on the Feast of Trumpets or Day of Atonement, but no-one knows for certain.