冬至是二十四节气的第二十二个节气，也是阳历年的最后一个节气。冬至俗称冬节、长至节或亚岁，自古以来一直都是非常重要的中国传统节日。今年的冬至始于12月22日。
冬至这天，太阳直射地面的位置到达一年的最南端，太阳几乎直射南回归线（又称为冬至线），阳光对北半球最为倾斜。因此，冬至日是北半球各地一年中白昼最短的一天，并且越往北白昼越短。
冬至是最早被制订的一个节气。古人认为自冬至起，白昼一天比一天长，天地之间的阳气开始兴作渐强，代表下一个循环的开始，是大吉之日。
从冬至当日起，每隔九天作为一个“九”，有九个“九”，共81天。这81天是全年最冷的一段时间，过后便迎来春天。民间有贴九九消寒图的习俗，有些用于记载入九之后的阴晴，有些是通过每日写一笔来度过九九。
先秦以冬至为岁首，君王每逢冬至便不再过问国政。汉朝时称冬至为“日至”,官场要举行贺节之仪，并放假休息，民间则要给父母尊长拜节。
冬至经过数千年的发展，形成了独特的节令食文化，吃饺子则是多数中国人冬至的习俗，在北方尤其突显。谚云：“十一月，冬至到，家家户户吃水饺。”
The traditional Chinese lunar calendar divides the year into 24 solar terms. Winter solstice, the 22nd solar term, is the last solar term in 2017. Winter solstice begins on Dec 22 this year.
Winter solstice marks the day with the shortest period of daylight and the longest night of the year. The seasonal significance of winter solstice is in the reversal of the gradual lengthening of nights and shortening hours of daylight during the day. 
Winter solstice was one of the first solar terms created in ancient China. People in ancient China observed that daytime became longer after winter solstice, which made it a very auspicious day as it signalled a new beginning.
Ancient Chinese people divided 81 days after winter solstice (regarded as coldest time of the year) into 9 parts. Many used "double-nine" diagrams to count the days to spring, either by recording the weather or writing one stroke of a character on a daily basis.
Winter solstice has always been an important festival in China. It was viewed as New Year's day in Qin Dynasty (221-206 BC). During Han Dynasty (206 BC-220), officials took the day off and participated in festive activities, where as civilians paid respects to their elders. 
China has developed an unique festive food culture throughout the years. Eating dumplings is a common folk custom for many Chinese on the day of winter solstice, especially those living in the north. 
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