Two of the most popular festivals celebrated by the pagan Romans were Saturnalia and Brumalia, in honour of Saturn and his son Jupiter, also known as Sol, the sun-god. They celebrated the shortest day of the year ( the winter solstice) and the death of the old sun and welcome the "new sun".
Their celebratory practices included kissing under the mistletoe as a prelude to unrestrained merrymaking, revelry and various hedonistic debauchery. They lit fires and candles to encourage the waning sun-god as he reached the lowest place in the southern skies.They hang wreaths at places of worship and their homes during these feasts. They also interchanged presents between friends. One of the symbols of their celebration was a "yule" ,"wheel", a pagan symbol of the sun.
These festivals originated from the ancient pagan Babylon which was established shortly after the great Flood of Noah's time and started by a mother and son who married each other, Semiramis and Nimrod (also known as Tammuz) . When he died, his mother-wife propagated the doctrine that he was still alive as a spirit being symbolised by a full-grown tree that sprang overnight from a dead tree stump, and that he would visit the tree and leave gifts upon it.
As you might have guessed, Saturnalia was celebrated on December 17 to 24 and Brumalia on December 25. And Nimrod's birthday was on December 25.
In the fourth century AD, King Constantine of Rome for political purposes integrated the fast-growing Christian religion which was then causing him great trouble and unrest (because of their refusal to observe pagan festivals), placing it on an equal footing with paganism. To placate his people who grievously resented this new religion and were vehemently unwilling to give up their own idolatrous festivities of revelry and drunken debauchery, Constantine "christianised" Saturnalia and Brumalia by declaring Dec 25 as the birth of Jesus Christ, instead, and renaming the celebration as Christ's mass, in honour of the "son" instead of the "new sun".
And that is how "Christmas" became fastened on the Western world.
The Nimrod tree is now known as the Christmas tree. The wheel,or "yule" as in yuletide season, yuletide greetings, the kissing under the mistle toe, the holly wreaths, the gift-giving to each other, the lighting of fires and candles, all symbols of the worship of the pagan sun-god are still actively used in the celebration of this repackaged heathen festival. The other symbols evolved later.
Saturnalia and Brumalia are now called by another name - Christmas - but it is the same old pagan sun-worshipping festival still.
Besides, Christ was not born any where near December 25.
References:The Catholic Encyclopedia 1911 edition
Encyclopedia Americana 1944 edition
The New Schaff-Herzog Encyclopedia of Religious Knowledge
Biblitheca Sacra Vol 12 pp 153-155
The Truth About Christmas, P Ardagh 2003 editionAnswers to Questions F J Haskins
The Plain Truth about Christmas 1974 edition