Dong Chi and Tet Dong Chi: the shortest day of the year, che troi nuoc, ancestor worship, and why Dong Chi was once the year's starting point

What is Dong Chi and when does it fall in 2025?

Dong Chi is the 22nd of the 24 solar terms, marking the moment when the Sun is farthest south of the celestial equator. It is the shortest day and longest night of the year in the Northern Hemisphere. In 2025, according to the perpetual calendar, Dong Chi falls on Sunday, December 21, corresponding to the 2nd day of the 11th lunar month.

This phenomenon occurs because the Earth's axis is tilted about 23.5 degrees relative to its orbital plane around the Sun. At Dong Chi, the Northern Hemisphere receives the least sunlight, resulting in a short day and long night. The Dong Chi solar term lasts from December 21, 2025 to January 4, 2026, followed by Tieu Han on January 5, 2026.

In Vietnam, Dong Chi often coincides with the coldest spells of winter. Temperatures drop significantly, especially in the northern mountainous regions. This is when farmers must protect crops, shelter livestock, and keep animals warm to avoid damage from harsh weather.

Why is it called Tet Dong Chi?

According to folk belief, there are four important traditional Tet holidays corresponding to the four seasons: Tet Nguyen Dan in spring, Tet Doan Ngo in summer, Tet Trung Thu in autumn, and Tet Ha Nguyen in winter. The name Tet Dong Chi follows Chinese cultural usage. For the Chinese community, it is a reunion festival, a time for family gatherings, eating che troi nuoc and banh to.

For Chinese people, Tet Dong Chi signifies welcoming the new year and bidding farewell to the old. Many still count age and dates using Dong Chi as a milestone. For example, a person aged 40 (lunar) in the At Ty year is considered to have turned 41 after Dong Chi of that year, which is December 21, 2025. Of course, this way of counting dates and age is only cultural in meaning.

How was Dong Chi once the year's starting point?

In East Asian tradition, Dong Chi was once considered the starting point of the yearly cycle. This belief stems from Dong Chi being the transition point when daylight begins to lengthen again after the longest night. Many ancient cultures regarded this as the rebirth of the Sun, beginning a new cycle.

The custom of counting age from Dong Chi reflects remnants of that belief. Instead of waiting for Tet Nguyen Dan, some communities use Dong Chi as the boundary to add a year of age. This custom is not common among Vietnamese people in general but still exists in the Chinese community and some Chinese-origin families in Vietnam.

Che troi nuoc and banh to in Tet Dong Chi

Che troi nuoc is a dish closely associated with Tet Dong Chi in the Chinese community. During this occasion, markets with large Chinese populations such as Cho Lon are busy selling che troi nuoc. This sweet soup symbolizes reunion and gathering, as the round dumplings sit together in a bowl of sweet broth.

Besides che troi nuoc, banh to is also a traditional dish during Tet Dong Chi. People also prepare hot dishes such as porridge and red bean soup to keep warm in the chilly weather. This is also a time for families to gather and share warm moments.

Ancestor worship on Dong Chi

For the Chinese community, Tet Dong Chi is an occasion for ancestor worship and remembering ancestors. The ceremony is usually held in the warm atmosphere of the family, with traditional dishes such as che troi nuoc and banh to. This cultural feature expresses filial piety and connection between generations.

In Vietnam, although Dong Chi is not a major holiday for the entire population, it remains an important occasion for the Chinese community and some Chinese-origin families to gather and practice traditional rituals. Families often prepare a simple but solemn offering tray, showing respect for ancestors.

Dong Chi in agriculture and weather

In Vietnam, Dong Chi marks the most distinct transition to winter. At this time, temperatures often drop deeply, especially in the northern mountainous regions. This is the period of severe cold, directly affecting agricultural production and livestock.

Farmers need to proactively protect crops, shelter livestock, and keep animals warm to avoid damage from harsh weather. Folk experience shows that good preparation before and during Dong Chi helps reduce risks for crops and livestock throughout the winter.

Dong Chi in the 24 solar terms

Dong Chi is the 22nd of the 24 solar terms. After Dong Chi, there are two more solar terms: Tieu Han and Dai Han, then the new year begins with Lap Xuan. The 24 solar terms reflect the movement of weather according to the solar cycle, long used in East Asian agriculture and daily life.

Understanding Dong Chi correctly helps distinguish between astronomical phenomenon and cultural meaning. Dong Chi is not a mandatory holiday for all Vietnamese people, but it is an important part of folk knowledge about weather and seasons. For the Chinese community, it is an occasion for reunion, ancestor worship, and enjoying traditional dishes that symbolize togetherness.