Short answers, pulled from the story.
The English word Christmas is a shortened form of Christ's Mass, first recorded in 1038 and again in 1131. This term derives from Middle English, combining the Greek word for Christ with the Latin word for celebration of the Eucharist.
Pope Julius I, bishop of Rome from 337 to 352, formally set the date. The earliest document placing Jesus's birthday on December 25 is the Chronograph of 354, also known as the Calendar of Filocalus, which reads that Christ was born in Bethlehem on VIII kal. Ian., consistent with Rome in AD 336.
In 1843, Charles Dickens wrote the novel A Christmas Carol, which helped revive the spirit of Christmas and seasonal merriment. Its instant popularity played a major role in portraying Christmas as a holiday emphasizing family, goodwill, and compassion.
On the 28th of June 1870, Christmas was formally declared a United States federal holiday. Louis Prang introduced the Christmas card to Americans in 1875, earning him the title father of the American Christmas card.
Nativity plays began in AD 1223 when Francis of Assisi assembled a scene outside his church in Greccio, Italy. Nativity scenes are known from 10th-century Rome and were popularized by Saint Francis of Assisi from 1223, quickly spreading across Europe.