TL;DR: Tiểu Hàn (小寒, meaning minor cold) is the 23rd of the 24 solar terms, at solar longitude 285 degrees. In Vietnam time it begins on January 5 or 6 and lasts about 14 days and 17 hours, until Đại Hàn begins. It opens the twelfth lunar month, the Sửu month in Bát Tự. In northern Vietnam this is a period of strong cold air, low humidity, little rain, and dry soil. The Vietnamese have no ritual of their own for this term; old Chinese books such as Tuế thời quảng ký record only calendrical statements and its three pentads: wild geese turning north, magpies building nests, pheasants calling.
What is Tiểu Hàn and why does it have that name?
Tiểu Hàn is the 23rd solar term in the system of 24 solar terms, coming right before Đại Hàn and after Đông Chí[1]. The name is written in Chinese characters as 小寒, where 小 (tiểu) means small and 寒 (hàn) means cold, so it can be translated closely as "mild cold". This way of naming reflects the relative degree of cold in the weather observations of the ancients: the cold is already clear but has not yet reached the harsh level of the Đại Hàn that follows[1].
Tuế thời quảng ký (歲時廣記) by Trần Nguyên Tịnh of the Southern Song, in its entry for the last month of winter (季冬月), quotes the Tam thống lịch to explain this pair of names: "小寒大寒者，十二月極寒之時，相對為大小，月初寒為小，月半寒為大", meaning the two terms are the coldest time of the twelfth month, with the cold at the start of the month called minor and the cold in the middle of the month called major[2].
In the modern calculation that takes the Xuân Phân point as the origin with a solar longitude of 0 degrees, the starting point of Tiểu Hàn corresponds to a solar longitude of 285 degrees[1].
When does Tiểu Hàn begin and how long does it last?
In Vietnam time, Tiểu Hàn begins on January 5 or 6: from 1900 to 2100, 102 years fall on the 5th and 93 years on the 6th; only 1904 falls on the 7th, and five years from 2081 to 2097 fall on the 4th. The term ends when Đại Hàn begins, usually on January 20 (in some years the 19th or 21st).
The solar terms are not equal in length, ranging from about 14.7 to 15.7 days, because the Earth moves faster or slower along its orbit. Tiểu Hàn is among the shortest, at about 14 days and 17 hours.
Start times of Tiểu Hàn in the coming years, in Vietnam time (UTC+7):
| Year | Solar calendar date | Start time |
|---|---|---|
| 2025 | January 5 | 9:30 |
| 2026 | January 5 | 15:18 |
| 2027 | January 5 | 21:05 |
| 2028 | January 6 | 2:54 |
| 2029 | January 5 | 8:42 |
| 2030 | January 5 | 14:32 |
The table below summarises the position of Tiểu Hàn in relation to the neighbouring terms:
| Solar term | Order | Solar longitude | Usual start date |
|---|---|---|---|
| Đông Chí | 22 | 270 degrees | December 22 (some years the 21st or 23rd) |
| Tiểu Hàn | 23 | 285 degrees | January 5 or 6 |
| Đại Hàn | 24 | 300 degrees | January 20 (some years the 19th or 21st) |
| Lập Xuân | 1 | 315 degrees | February 4 (some years the 3rd or 5th) |
What is worth noting about the weather of Tiểu Hàn in Vietnam?
After Đông Chí, the point where the Sun shines directly overhead has begun to move gradually northward, but temperatures in the Northern Hemisphere do not rise right away. During Tiểu Hàn, temperatures in many regions drop to their lowest level of the year[1]. In the northern provinces of Vietnam, cold air is frequently active during this period, but relative humidity is low so rainfall is usually scarce[1].
Those dry and cold conditions make the ground surface dry easily, with a certain effect on the growth of crops[1]. On January 5, 2026, the National Centre for Hydro-Meteorological Forecasting predicted intensified cold air, with some high mountain areas in the north seeing cold of around 5 degrees Celsius, affecting the Northeast, North Central, Northwest and Central Central regions[1].
People living in areas affected by cold air need to pay attention to keeping the body warm and to maintaining a suitable diet during this term[1]. In agriculture, severe and damaging cold can affect the yield of crops and livestock, so farmers need to take proactive measures against the cold[1].
What customs does Tiểu Hàn have?
Tiểu Hàn is not a traditional Tet day of the Vietnamese people, and the Vietnamese have no ritual of their own for this term.
In its entry for the last month of winter, Tuế thời quảng ký records calendrical statements and the three pentads of Tiểu Hàn, not any custom of its own. It quotes the Chu thư Thời huấn: "小寒之日雁北嚮，又五日鵲始巢，又五日雉始雊", meaning that on the day of Tiểu Hàn the wild geese turn north, five days later the magpies begin to build nests, and five days after that the pheasants begin to call[2].
In folk understanding, Tiểu Hàn is often mentioned as the marker of the start of the coldest period of winter, along with reminders to keep warm, eat hot food and limit going outside in the early morning. This is an understanding based on lived experience, not a fixed ritual with its own date, time and offerings.
Why is Tiểu Hàn important in Eastern calendrics?
The solar terms are a system of dividing the year by the position of the Sun, different from the division by lunar phase of a purely lunar calendar. The system of 24 solar terms helps farmers determine the farming season, while in divination and feng shui it is one of the bases for placing stars, choosing days and calculating the energy of a period.
In the same entry, Tuế thời quảng ký quotes the Tam thống lịch: "小寒為十二月節，大寒為十二月中氣", meaning Tiểu Hàn is the term that opens the twelfth month and Đại Hàn is the month's mid-term; it also quotes the Hiếu kinh vĩ: "冬至後十五日斗指癸為小寒", meaning that fifteen days after Đông Chí, when the handle of the Big Dipper points to the Quý direction, it is Tiểu Hàn[2].
In Bát Tự, the month pillar changes at the 12 terms, not at the mid-terms, so from the moment Tiểu Hàn begins the month pillar shifts to the Sửu month, the twelfth lunar month, even though in some years the lunar date at that moment still belongs to the eleventh month.
The book Dịch tượng chính by Hoàng Đạo Chu of the Ming dynasty, in the sixth diagram of its opening volume, arranges the hexagrams by season: Tấn corresponds to Lập Hạ, Minh Di to Lập Đông, Lâm to Xuân Phân and Quan to Thu Phân, and it calls Càn the extreme of heat and Khôn the extreme of cold[3]. This is a convention of the tradition that uses the I Ching to speak of the calendar, not a verified research result.
How does Tiểu Hàn differ from Đại Hàn?
Đại Hàn is the last solar term of the year, continuing right after Tiểu Hàn[1]. By its naming, Đại Hàn implies a harsher degree of cold, and in reality this is an even colder period, with no small effect on the yield of crops and livestock[1].
The distinction between the two terms is mainly relative and conventional, because the actual degree of cold also depends on each year and each region. In northern Vietnam, both terms fall within the peak period of winter, so measures against the cold are usually maintained continuously through both terms rather than separately.
Nhật Nguyệt's suggestions for looking up Tiểu Hàn
When you need to look up Tiểu Hàn for a specific year, you should use a calendar that records solar terms or an astronomical table to determine the exact start date, rather than applying a fixed date to every year. If you use solar terms for the purpose of choosing days or placing stars, you need to determine clearly which school's convention you are following, because books may attach Tiểu Hàn to different directions or hexagram images. For keeping warm and protecting crops and livestock against the cold, information should be taken from the meteorological forecasts of the relevant authorities in the year under consideration.
