Dàhán

Dahan, Major Cold, is the twenty-fourth and final solar term, at the sun's longitude of 300 degrees, around the twentieth of January. It is a principal (zhongqi) term and traditionally the coldest point of the year, the extreme of winter. After it the cycle returns to Lichun and the start of spring, closing the round of twenty-four terms. In the farming almanac it is a time of final preparation for the new year and the coming season, often coinciding with the busy run-up to the Lunar New Year, with the making of festival foods and the setting of the household in order. Being a solar marker, it falls near the same Gregorian date each year. These are the observances of the East Asian agricultural tradition, resting on the astronomical division of the tropical year into twenty-four equal solar arcs.

Dahan, Major Cold, falls at 300 degrees of ecliptic longitude, around 20 January, and is a qi, or major, term, traditionally the last and, in principle, coldest of the twenty-four terms before the cycle closes and returns to Lichun, the Start of Spring, fifteen degrees and roughly two weeks later. Dahan falls close to the Chinese Lunar New Year in most years, since the lunisolar calendar's intercalation keeps the new year anchored to the second new moon after Dongzhi, the winter solstice, and the term is traditionally treated as the period for final preparations, cleaning the home, preparing festival foods and settling debts, before the year's most important festival begins.

The twenty-four solar terms divide the ecliptic into equal arcs of fifteen degrees, and this one falls at 300 degrees of the sun's apparent longitude. It is a major term, a zhongqi, one of the twelve that fall in the even positions of the twenty-four. The major terms are the ones that anchor the lunar months, and they alternate strictly with the sectional terms, so a zhong is always followed by a jie fifteen degrees later.

The system travelled with the Chinese calendar. Japan, Korea and Vietnam all adopted the twenty-four terms and kept their own readings of the same names, and the terms remain in use in each. In 2016 the twenty-four solar terms were inscribed on the UNESCO Representative List of the Intangible Cultural Heritage of Humanity, on the ground that they remain a living framework for agricultural and everyday practice rather than an obsolete scheme.

Dahan, major cold, is the twenty-fourth and last of the terms, and the sun's arrival at 315 degrees immediately afterwards returns the cycle to Lichun. The list therefore closes at the coldest point and opens at the establishment of spring, which places the boundary of the solar year at a climatic low rather than at an astronomical event, a choice that distinguishes the Chinese scheme from calendars that begin at a solstice or an equinox.