Christmas is the 'Mass of Christ'(Mass being a religious festival) and is the time when Christians everywhere celebrate the Nativity (birth) of Jesus Christ. Because Jesus was born more than 2000 years ago, and before accurate records were kept, we are not sure of His exact date of birth. But.. shepherds brought their lambs, so it may have been springtime. Nevertheless, late December was already special, as it was when people paid their thanks for the return of longer day- light after the winter solstice. We know from the Bible that Jesus was born in Bethlehem. Mary and Joseph had travelled from Nazareth to Bethlehem for the Roman census. Christmas has been celebrated by Christians since approximately 400 A.D.