Dongzhi occurs at celestial longitude 270°, around December 21-23. The longest night and shortest day of the northern hemisphere year. Classical wisdom: "冬至一陽生" — at the depth of winter, yang is reborn. The "nine-nine" cold-day count begins.
Tradition: northern China eats dumplings; southern China eats glutinous rice balls (湯圓). Family reunion is emphasized — "冬至大如年" (winter solstice is as important as new year). Climate: coldest period still ahead.
The phrase about a single yang being born at the solstice is not from the Book of Changes itself but from Han-dynasty calendrical Yi learning: the twelve sovereign hexagrams assign the Zi month to Fu (復, Return), a single yang line stirring beneath five yin lines; the Commentary on the Judgement adds that in Return one may glimpse the heart of heaven and earth. The Great Image commentary says that thunder lies within the earth, and that the former kings therefore closed the passes on the solstice day, so that merchants did not travel and the sovereign did not tour the regions. Those lines are the classical warrant for shutting down business at Dongzhi.
No other solar term carries as much weight in the history of Chinese calendars. Dongzhi (冬至 Dōng Zhì) was the origin point for astronomical computation: measure the interval between successive solstices and you have the length of the tropical year. Guo Shoujing observed solstices over years while compiling the Shoushi calendar of the Yuan dynasty, arriving at 365.2425 days. The modern lunisolar calendar still anchors on it — the lunation containing the solstice is by definition the eleventh month, and leap months are placed around that fixed point.
Whether the year pillar changes at the solstice is among the most common questions, and in current Bazi practice the answer is no — the year turns at Lichun. The confusion has a real historical root. The Zhou calendar took the month containing the solstice as the year's first month; the Qin began the year with the Hai month; and only with Emperor Wu of Han's Taichu reform was the Yin (寅) month fixed as the first, as it remains. The doctrine of the three first months records exactly this disagreement between dynasties. Old systems and current usage are not interchangeable.
Dongzhi is a mid-term and changes no pillar: the Zi month runs from Daxue to Xiaohan, with the solstice at its centre. Its significance in reading a chart is therefore not as a boundary but as a fixed point in the waxing and waning, where daylight turns from shortening to lengthening and the direction of the cold reverses. Traditional practice notes whether a Zi-month birth fell before or after the solstice: yin still increasing in the first case, yang already under way in the second. This refines the reading of the qi without altering the pillar or the structure.
Shortest daylight does not mean lowest temperature. The surface receives the least solar radiation that day, while land and ocean continue releasing heat banked earlier, and the balance does not bottom out for another thirty or forty days. The lowest temperatures in most places arrive between Xiaohan and Dahan. The folk practice of counting nine nines, eighty-one days forward from the solstice, concedes the same point: the worst of the cold is still ahead.
A second divergence around the solstice concerns where the day begins. The Zi hour spans 23:00 to 01:00. One position assigns the whole Zi hour to the following day; another holds that the late Zi hour, 23:00 to midnight, still belongs to the current day while the early Zi hour, midnight to 01:00, belongs to the next. Someone born near the solstice and within the Zi hour may see both the day pillar and the hour pillar affected. Charting software differs in its default, so the setting is worth confirming before trusting a result.
The saying that the solstice is as great as New Year has substance behind it. Han-dynasty offices suspended business and held congratulatory observances around the solstice, and later eras kept the rites of ancestral offering, seasonal greeting and the issuing of the official calendar. The nine-nine cold-dispelling chart is another widespread habit: from the solstice one fills in a single petal of an eighty-one-petal plum drawing each day, and when the drawing is complete spring has arrived — an abstract count made visible. Dongzhi and the summer solstice stand opposite each other as Zi and Wu, one the birth of yang and the other the birth of yin.
No. The solstice has the shortest daylight and the lowest sun, so the surface receives the least solar energy — but land and sea keep releasing heat stored earlier, and the energy balance does not reach its lowest point for another thirty to forty days. The coldest stretch usually falls between Xiaohan and Dahan. The folk count of eighty-one days forward from the solstice takes it for granted that the deep cold comes afterwards.
Not in current Bazi practice. The year turns at Lichun, and the solstice is a mid-term that does not even change the month pillar. The question arises because some historical calendars really did begin the year with the month containing the solstice, as the Zhou calendar did; the Qin began with the Hai month, and the Yin month became standard only after the Han Taichu reform. The idea has a genuine pedigree, but it is not the convention modern charts use.
It refers to the hexagram Fu (復), assigned to the Zi month among the twelve sovereign hexagrams: a single yang line appearing beneath five yin lines. The image describes a turning point in the alternation of yin and yang, with yin reaching its maximum and beginning to recede while yang restarts from the very bottom. Astronomically this corresponds to daylight beginning to lengthen. It describes a reversal of trend, not an immediate warming.
Because it is one of the most precisely measurable astronomical moments, it served as the computational origin for successive Chinese calendars: the interval between two solstices gives the length of the tropical year. Guo Shoujing observed it over many years for the Yuan-dynasty Shoushi calendar. The modern lunisolar calendar also fixes the lunation containing the solstice as the eleventh month and arranges intercalation around that anchor, so the solstice sets the calendar's skeleton.
It depends on the region, not on correctness. Northern China favours dumplings; the lower Yangtze, Fujian and Taiwan favour tangyuan or solstice rice balls; parts of Guangdong prepare roast meats and glutinous rice. These reflect local produce and food tradition, and none is more orthodox than another. What they share is the theme of reunion and ancestral offering, which is why the solstice was long treated as nearly equal to New Year.
They are the year's most symmetrical pair. Dongzhi falls at 270° of solar longitude with the shortest daylight; the summer solstice falls at 90° with the longest, half a year apart. In the branch system they are Zi and Wu, which stand in direct opposition. Among the twelve sovereign hexagrams the winter solstice takes Fu, one yang born below, and the summer solstice takes Gou (姤), one yin born below — one turning toward warmth, the other toward cool.