On this day, over 2 billion people (over a third of the world's population) will celebrate the birth of Christ.
Christmas Day celebrates the Nativity of Jesus which (traditionally, but unlikely in reality) took place 25 December 1 BC. 25 December will be a public holiday in most countries around the world. If 25 December falls on a weekend, then a nearby week day may be taken as a holiday in lieu. For a list of countries who have holidays over the Christmas period, check our 2015 Christmas dates list.
Not all countries celebrate Christmas on 25 December, and it is not a public holiday in many countries. Read 'Christmas Day around the world' for more details.
Whilst the holiday has a strong grounding in the story of the birth of Jesus, many of the traditions we associate with Christmas have evolved from pre-christian beliefs and certainly the traditions have evolved beyond purely a Christian holiday to have a wider secular significance.
The celebration of Christmas in late December is certainly as a result of pre-existing celebrations happening at that time, marking the Winter Solstice.
Most notable of these is Yule (meaning 'Feast'), a winter pagan festival that was originally celebrated by Germanic people. The exact date of Yule depends on the lunar cycle but it falls from late December to early January. In some Northern Europe countries, the local word for Christmas has a closer linguistic tie to 'Yule' than 'Christmas', and it is still a term that may be used for Christmas in some English-speaking countries. Several Yule traditions are familiar to the modern celebration of Christmas, such as Yule Log, the custom of burning a large wooden log on the fire at Christmas; or indeed carol singing, which is surprisingly a very ancient tradition.
Did you know?
22% of men leave their Christmas shopping until the last two days before Christmas. Only 9% of women do the same. And 12% of us don't even start our Christmas shopping until the January sales.
More Christmas Day facts
Under the Julian calendar, the winter solstice was fixed on December 25, and this date was also the day of the popular roman holiday of Saturnalia, in honour of Saturn, the god of agriculture; which was later superceded by Sol Invictus, a day that bundled up the celebration of several sun based gods into one easy to manage festival.
As Christianity began to take a hold across the Roman empire and beyond, the date of when to celebrate the birth of Christ became a bit of an issue, with several different dates proposed.
It wasn't until 350 AD, when the then Bishop of Rome, Pope Julius I, fixed the official Christmas day on December 25. Unfortunately Julius I didn't show his working out on how he reached this date; some scholars later suggested that it was calculated as nine months after the Annunciation (March 25), when the angel Gabriel is said to have appeared to Mary and told her she would bear the son of God. Whatever the reasoning, it is clear that, just as key pagan sites were being chosen for new churches, so too the date was chosen with the intention to catapult Christmas into becoming a major festival by placing it over the pre-existing pagan festivals.
Did you know? The use of 'Xmas' isn't necessarily a secularisation of Christmas; it is said to date from the ancient practice of using a cross as a symbol for the word 'Christ'.
More Christmas Day facts
Kissing someone who happens to being stood under a sprig of mistletoe is seen as a tradition popularised in Victorian England. However even this relatively modern tradition has much more ancient echoes in that Mistletoe bears its fruit around the time of the Winter Solstice, and its supposed mythical ability to heal and increase fertility.
Another hint of its integration from pagan ceremonies into Christmas tradition is said that the mistletoe plant used to be a tree, and its wood was used to make the Cross on which Jesus was crucified. After the Crucifixion, the plant shriveled to became the parasitic vine we know today.
As mentioned earlier, the tradition of singing of songs can be traced back to the pagan festivals before the advent of Christmas. Indeed, the word carol is derived from the Greek word choraulein, which meant "an ancient circle dance performed to flute music."
As carols were already an established custom, early Christians made the shrewd decision to integrate Christian songs into the tradition rather than ban the singing.
Most new Christian Carols were written in Latin, which was by the middle ages, a language only used by the church, thus reducing the popularity of the custom.
However, carols received an injection of popularity when St. Francis of Assisi started his Nativity Plays in Italy in 1223, which included songs written in the local people's language.
The tradition of 'Modern' Carol singing flourished in England. Known as Wassailing, it was a chance for peasants to get some much needed charity from their feudal lords. This singing for money developed in a custom involving traveling musicians who would visit wealthy homes, singing in the hope of receiving money food or gifts in return.
There was a short interruption in 1647, when the puritans come to power after the English Civil War. The puritans, under the leadership of Oliver Cromwell, disapproved of the celebration of Christmas. There was even a fine of up to five shillings for anyone caught singing Christmas carols. When King Charles II came back to the throne in 1660, the public singing of Christmas carols was permitted again.
Christmas is called 'Jul', derived from Yule. Christmas starts with advent, the fourth Sunday before Christmas Eve. A wreath with four candles and ribbons is hung up and one candle is lit. Another candle is lit on each of the following Sundays before Christmas.
A law often quoted in regards to Christmas is the Holy Days and Fasting Days Act of 1551, which said that everyone in England must attend church on Christmas Day without using any form of transport. Rather disappointingly this law was repealed in 1969.
Alabama was the first US state to legalise the celebration of Christmas. The last state to make Christmas a legal holiday was Oklahoma in 1907.
The White House had its first Christmas tree in 1856. It was decorated by US president Franklyn Pierce.