It is estimated that Christmas has been celebrated since around 300 AD. However, many of the customs connected to Christmas as we celebrate it today may actually have roots in December celebrations which were held as much as 4000 years ago around the winter solstice - the Romans had Saturnalia and the Germanic peoples honoured the god Odin. As the Bible does not give enough clues as to when Jesus Christ was born, many believe that the date was borrowed from the earlier pagan festivals.
Today, the Christmas tree and presents are probably the two most recognisable elements of Christmas. But both of these haven’t really been around for that long. In Britain, the tradition of decorating the Christmas tree was introduced in the early 19th century. In America, it became common in the second half of the century. It seems that gift-giving is relatively new, too - presents entered Christmas celebrations more or less at the same time as Christmas trees.