Christmas Day-December 25-which celebrates the birth of Jesus Christ， the founder of the Christian religion， is the biggest and best-loved holiday in the United States.
According to the Bible， the holy book of Christians， God decided to allow his only son， Jesus Christ， to be born to a human mother and live on earth so that people could
understand God better and learn to love God and each other more. "Christmas"- meaning "celebration of Christ "- honors the time when Jesus was born to a young Jewish woman Mary.
Mary was engaged to be married to Joseph， a carpenter， but before they came together， she was found to be with child. Because Joseph， her husband， was a righteous man and did not want to expose her to public disgrace， he had in mind to
divorce her quietly. But after he had considered this， an angel of the Lord appeared to him in a dream and said， "Do not be afraid to take Mary home as your wife， because
what is conceived in her is from the Holy Spirit. She will give birth to a son， and you are to give him the name Jesus， because he will save his people from their sins."
Although the exact date of the birth of Jesus nearly 2，000 years ago is not known， the calendar on the supposed date divides all time into B.C. (Before Christ )and A.D.
( a Latin phrase， Anno Domini， "in the year of our Lord.")For the first 300 years， Jesus’ birthday was celebrated on different dates. Finally， in the year 354， church leaders chose December 25 as his birthday.
圣诞节只是基督徒庆祝其信仰的耶稣基督(jīdū)诞生的庆祝日。圣诞节的庆祝与基督教同时产生，被推测始于西元1世纪。很长时间以来圣诞节的日期都是没有确定的，因为耶稣确切的出生日期是存在争议的，除了《新约》以外，没有任何记载提到过耶稣;《新约》不知道日期，当然就没有人知道确切日期了。
在西元后的头三百年间，耶稣的生日是在不同的日子庆祝的。西元3世纪以前的作家们想把圣诞日定在春分日上下。直到西元3世纪中期，基督教在罗马合法化以后，西元354年罗马主教指定儒略历12月25日为耶稣诞生日。现在的圣诞节日期跟西元纪年的创制是密不可分的。
西元纪年创制于西元5世纪，后来圣诞节这一天就按格里高利历法，即西元纪年的“公历”来确定了，而日历按着假定日期把时间分为公元前(耶稣基督诞生前)和公元后(A. D. 是拉丁文缩写，意思是“有了我们主--耶稣的年代”)。
后来，虽然普遍教会都接受12月25日为圣诞节，但又因各地教会使用的历书不同，具体日期不能统一，于是就把12月24日到第二年的1月6日定为圣诞节节期(Christmas Tide)，各地教会可根据当地具体情况在这段节期之内庆祝圣诞节。西方教会，包括罗马天主教、英国圣公会和新教，确定的圣诞日是公历的12月25日。
东正教会确定的圣诞日是公历1月7日(实际上是叫“主显日”)，这与东正教没有接受格里高利历改革和接受修正后的儒略历有关，因此把圣诞节在1900年到2099年的这一段时间内将延迟到1月7日。保加利亚和罗马尼亚也是东正教区，但圣诞节日期上遵循西欧习惯为12月25日，但复活节则遵从习惯。
而最古老的基督教会亚美尼亚使徒教会确定的是公历1月6日，同时亚美尼亚教会更关注主显节，而不是圣诞节。圣诞节也是西方世界以及其他很多地区的公共假日，例如：在亚洲的香港、马来西亚和新加坡。世界上的非基督徒只是把圣诞节当作一个世俗的文化节日看待。
教会开始并无圣诞节，约在耶稣升天后百余年内才有。据说：第一个圣诞节是在公元138年，由罗马主教圣克里门倡议举行。而教会史载第一个圣诞节则在公元336年。
由于圣经未明记耶稣生于何时，故各地圣诞节日期各异。直到公元440年，才由罗马教廷定12月25日为圣诞节。公元1607年，世界各地教会领袖在伯利恒聚会，进一步予以确定，从此世界大多数的基督徒均以12月25日为圣诞节。十九世纪，圣诞卡的流行、圣诞老人的出现，圣诞节也开始流行起来了。
Although, for Christians, Christmas is not the most important of festivals, it is probably the most widely celebrated religious occasion in the West. This festival celebrates the birth of the messiah in Bethlehem Palestine about two thousand years ago. This messiah was Jesus Christ who, Christians believe, was sent to save mankind and absolve them from their sins. Nowadays, you might be forgiven for missing the religious element to this festival as it has descended somewhat into an orgy of consumerism and indulgence. Gifts are given amongst family and friends and cards wishing “Seasonal Greetings” sent between just about everyone. Father Christmas, otherwise known as Santa Claus, is said to squeeze his way down chimneys across the world on Christmas Eve and deliver presents to any children that have behaved well over the last year. Another important motif of the festival is the Christmas tree, around which traditionally people would dance around hinting at the pagan origins of this mid-winter celebration.
圣诞节
虽然对基督教徒来说，圣诞节并不是其最重要的节日，但是在西方，它却是一个最受广泛庆祝的节日。圣诞节庆祝的是两千多年前弥赛亚(犹太人盼望的复国救主)在巴勒斯坦伯利恒的诞生。这个弥赛亚就是耶稣(基督教信奉的救世主)。基督教徒相信，耶稣是被派来拯救人类并协助人们摆脱罪恶的救世主。如今，就算你已经忘记了这个节日的本来意义也不会有人怪罪你，因为，现在的圣诞节已经演变成为大肆消费、狂欢与纵情享受的节日。在这个节日里，亲人们、朋友间都会互送礼物，满载着“节日祝福”的贺卡也会送到每一个人的手中。“圣诞之父”（Father Christmas），也就是我们所熟知的“圣诞老人”（Santa Claus），据说会在圣诞节前夕顺着烟囱下来，给世界各地的孩子们送去礼物，这些收到礼物的孩子必定是那些在过去的一年中各方面表现都很优秀的孩子。圣诞节的另一个重点是圣诞树，在这一天，人们会围着圣诞树跳舞，这也表明圣诞树是圣诞节形成之前的隆冬节日的重要组成部分。本回答被提问者采纳