THAT MEANS Christmas?
Christmas is a contraction of the word "nativity" which means "birthday" or "day of birth." Specifically, Christmas is only used to describe the birth of Christ. The specific date and accurate view of Christmas, that is the birth of Christ is unknown. Christmas is not registered by any historical source and, as you know, there are historical writings, ignoring the Gospels, doubted the existence of Jesus Christ. However, in the Roman tradition (then carried through the centuries by Christianity) was timed to coincide with Christmas that date on which the sun goes unbeaten against the darkness. In Rome, the festival of Sol Invictus "was celebrated on December 25, the day the autumn equinox step left to winter solstice. Until that day the winter solstice has waned and the darkness has been spreading. Christian tradition has done since Christmas to coincide with the day the darkness was defeated by the light of the day when daylight hours grow at the expense of hours of shade and night. Christmas was not a festival held since the beginning of the Church. Officially, the birth of Christ is celebrated on December 25 from the fourth century, under the rule of Emperor Constantine, with Pope

WHY HE CELEBRATES ?
In Western countries are traditionally celebrates the birth of Christ on Dec. 25. The customs vary, although many, like the Christmas tree and exchanging gifts, they are fairly distributed. On the other hand, the Christians of the Orthodox churches celebrate Christmas on 6 and Jan. 7, and the Armenian church on 18 and 19 of the same month. In fact the Gospels do not give the exact date for the birth of Christ. However, according to the text of the evangelists are unlikely to have been in winter, because pastoralists in the region remain in the fields only between spring and autumn. Moreover, it is not known exactly the year, because according to the Gospels took place during a Roman census, and there was no census in the first year of the Christian era. It also mentions the reign of Herod, but during his reign were not carried out censuses. The uncertainty is increased to 325 in the year replaced the Julian calendar, used in the Roman Empire, with the Gregorian, which is what we use today. The Romans counted the years since the founding of Rome in the year 753 BC, but the monk Dionisus Exiggus mistakenly took this date as the 748 a. C. The error was not detected until long after the introduction of the new schedule, so the date of the birth of Christ would be five years before what was thought. But that date also contradicts the figure of the Roman census. On Dec. 25 was defined as Christmas in the fourth century, more precisely in the year 345, under the influence of St. John Chrysostom and St. Gregory of Naciaceno. According to many versions that date was chosen to replace many holidays of pagan origin, such as Saturnales held by the Romans in honor of Saturn, who precidía agriculture. In this era were held large banquets and many shows. Others believe that the party was to replace the winter solstice, when the days begin to lengthen. This celebration was called "Natalis Solis Invicti", the birth of the Sun Conqueror. Another likely reason was to replace the birthday of the god Mithras, one of the most important mythology Zoroastrianism, which had much influence in the Roman Empire. This will replaced a pagan festival by a more in tune with the Christian religion. Since then, in the countries of the West is celebrated every December 25 as the date of Christmas