Christmas or Christmas Day (Old English for “Christ’s Mass) is an annual Christian holiday commemorating the birth of Jesus Christ. Christmas is central to the Christmas and holiday season. In Christianity, it marks the beginning of the larger season of Christmastide, which lasts twelve days.
Although a Christian holiday, Christmas is also widely celebrated by many non-Christians, and some of its popular celebratory customs have pre-Christian or secular themes and origins. Popular modern customs of the holiday include gift-giving, music, an exchange of greeting cards, church celebrations, a special meal, and the display of various decorations; including Christmas trees, lights, garlands, mistletoe, nativity scenes and holly. In addition, Father Christmas or Kris Kringle (better known to Americans as Santa Claus, as well as those in Australia and Ireland) is a popular folklore figure in many countries, associated with the bringing of gifts for children.
Because gift-giving and many other aspects of the Christmas festival involve heightened economic activity among both Christians and non-Christians, the holiday has become a significant event and a key sales period for retailers and businesses. The economic impact of Christmas is a factor that has grown steadily over the past few centuries.
While the month and date of Jesus’ birth are unknown, by the early-to-mid 4th Century, the Western Christian Church had placed Christmas on December 25th, a date later adopted in the East. Today, most Christians celebrate Christmas on the date of December 25th in the Gregorian calendar, which is also the calendar in near universal use in the secular world. However, some Eastern churches celebrate Christmas on the December 25th of the older Julian calendar, which currently corresponds to January 7th in the Gregorian calendar. This is not a disagreement over the date of Christmas, but rather a disagreement over which calendar should be used to determine the date that is December 25th. The date of Christmas may have initially been chosen to correspond with the day exactly nine months after the day on which early Christians believed that Jesus was conceived, or with one or more ancient polytheistic festivals. (from www.cute-calendar.com)