The traditional Chinese calendar divides a year into 24 solar terms.^[1] Dōngzhì, Tōji, Dongji, Tunji (in Okinawan), or Đông chí (in Vietnamese) is the 22nd solar term, and marks the winter solstice. The term begins when the Sun reaches the celestial longitude of 270° and ends when it reaches the longitude of 285°^{[disputed – discuss]}. In the Gregorian calendar, it usually begins around 21 December (22 December East Asia time) and ends around 5 January.

In common usage, Dongzhi more often refers to the particular day when the Sun is exactly at the celestial longitude of 270°.

Along with equinoxes, solstices (traditional Chinese: 至點; simplified Chinese: 至日; lit. extreme day) mark the middle of Traditional Chinese calendar seasons. Thus, in "冬至", the Chinese character "至" means "extreme", which implies "solstices", and therefore the term for the winter solstice directly signifies the summit of winter, as "midwinter" is used in English.

In China, Dongzhi was originally celebrated as an end-of-harvest festival. Today, it is observed with a family reunion over the long night. In southern China, pink and white tangyuan are eaten in sweet broth to symbolise family unity and prosperity, whereas in northern China, the traditional Dongzhi food is jiaozi.^{[citation needed]}

In Korea, the winter solstice is also called the "Small Seol," and there is a custom of celebrating the day. People make porridge with red beans known as patjuk (팥죽) and round rice cakes (새알심 saealsim) with sticky rice. In the past, red bean porridge soup was sprayed on walls or doors because it was said to ward off bad ghosts. In addition, there was a custom in the early days of the Goryeo and Joseon Period in which people in financial difficulty settled all their debts and enjoyed the day.^[2]

In Japan, the name of the solar term is Tōji. On this day, it is customary to drink grapefruit hot water and eat pumpkin in certain places. White flowers begin to bloom around the winter solstice.^{[citation needed]}

Each solar term is divided into three pentads which are typically named after seasonal natural events. The pentads during Dongzhi are:^{[citation needed]}

• 蚯蚓結, 'Earthworms form knots', referring to the hibernation of earthworms.
• 麋角解, 'Deer shed their antlers'
• 水泉動, 'Spring water moves'

• Dongzhi Festival
• Winter solstice