Seems your not looking for truth, that post said 110 nobel peace prize winners contributed. There is not a more reliable encyclopedia in the world.
But with the wave of a hand hundreds of peoples legit documentation work is dismissed...
The New International Dictionary of the Christian Church, Revised Edition, by Zondervan Publishing:
CHRISTIAN YEAR, THE. The early Christians who were mainly Jews were used not only to keeping one day in the week as separate but also to marking the year with certain religious festivals, notably Passover, Tabernacles, and Pentecost. From early times Christians kept a commemoration of Christ’s resurrection. This was held at Passover time and was finally fixed on the Sunday following Passover. Pentecost was then celebrated at the appropriate time; the fifty days between the two were days of joy and rejoicing. The choice of 25 December (in the East, 6 January) for the birth of Christ is almost certainly because that day was the great pagan day of honor to the sun, and in Rome in the fourth century it was transformed into a Christian festival. CHRISTMAS. The English name for the Feast of the Nativity of Christ kept on 25 December by the Western Church. There is no evidence of a Feast of the Nativity before the fourth century, except possibly among the Basilidians. Theearliestmentionof25 December is in the Philocalian Calendar, compiledin354, which cites its observance in Rome in 336. It would not appear to have been celebrated in Antioch until approximately 375. By380 it was being observed in Constantinople, and by 430 in Alexandria. It was still unknown in Jerusalem early in the fifth century__it was not until the sixth century that the Nativity was finally detached from 6 January and celebrated on 25 December. By the middle of the fifth century it was being gradually observed throughout East and West. The Armenians still observe 6 January, the closely related Feast of the Epiphany, as Christmas Day. There is no authoritative historical evidence as to the day or month of Christ’s birth in Jerusalem. 25 December was the date of a Roman pagan festival inaugurated in 274 as the birth day of the unconquered sun which at the winter solstice begins again to show an increase in light. Sometime before 336 the Church in Rome, unable to stamp out this pagan festival, spiritualized it as the Feast of the Nativity of the Sun of Righteousness. Christmas in the Eastern Church celebrates the birth of Christ together with the visit of the shepherds and the adoration o fthe wise men. In the Western Church the adoration of the Magi is attached to Epiphany on 6 January. In the Roman Catholic Church three masses are usually said to symbolize the birth of Christ eternally in the bosom of the Father, from the womb of Mary and mystically in the soul of the faithful. The traditional customs associated with Christmas have been derived from several sources. The merrymaking and the exchange of presents find their origin in the Roman Saturnalia festival (17-24 December), and the greenery and lights come from the Kalends of January (1 January, the Roman New Year) with its solar associations. The Germano-Celtic Yule rites introduced the tradition of feasting and fellowship. In the USA (and in England during the Commonwealth) Christian celebrations were at first suppressed by the Puritans, who objected to their pagan origins. Since the nineteenth century the celebration of Christmas has become increasingly popular.