1. Christmas is a festival celebrating the birth of Jesus Christ, the founding figure of Christianity. Its earliest mention as a regular festival of the Western or Roman church is in CE 336.
2. The date of December 25 was set on the basis of pagan festivals such as Saturnalia, a period of licence and excess at the end of the Roman year, and the northern European festivals around the time of the winter solstice on December 21.
3. These were often celebrated with feasts, gifts and donations to the poor. One tradition has it that the origin of giving gifts at Christmas time was the edict of a Roman emperor, who ordered debtors to pay their debts and fines at the end of the year.
4. December 25 was also traditionally the birthday of the Persian god Mithra, known as the Sun of Righteousness and Lord of Light. His cult spread to India and became a very popular men-only religion across the Roman empire (Mithras) in the first century BCE. Legend has it that Mithra's magic birth from a rock was witnessed by shepherds.
5. Various attempts have been made to calculate the precise date of Jesus's birth. The Bible gives no dates, only incompatible clues (Luke 1:5; 3:1, 2). It was the Scythian abbot Dionysius Exiguus, in the 530s CE, who calculated that Jesus must have been born in the 754th year since the foundation of Rome, which became 1CE ("Anno Domini" – "year of our Lord").
6. The oldest official mention of any date for Jesus's birth is in De Pascha Computus, a church document from the mid-200s CE designed to show how the dates for Easter could be worked out each year. It gave Christ's birthday as March 28.
7. Church father Clement of Alexandria (early 200s) is said to have believed Jesus was born on November 18.
8. The hugely popular Victorian novelist Charles Dickens is associated with the modern Christmas celebration. His novella A Christmas Carol, about the miser Scrooge who repents his miserliness, was a massive bestseller in 1843. After A Christmas Carol, Dickens produced a Christmas story almost every year until 1867. He died in 1870.
9. The origin of the Christmas tree lies in northern European pagan cults that worshipped in forests, as well as more general European year-end festivities in which houses were decked with greenery to symbolise new life.
10. The figure of Santa Claus is based on that of a Turkish bishop called Nicholas (270CE – 345CE), who was said to have given gifts to the poor at the coldest time of year. A cult to do with his holy relics spread and in northern Europe he was partly merged with the figure of Wotan, the white-bearded Scandinavian god. He was appropriated by the Catholic church and was made a saint in the 19th century.