TL;DR: Lập Đông (立冬) is the 19th solar term in the system of 24, marking the moment the Sun reaches 225 degrees of ecliptic longitude, usually on 7 or 8 November. It is the start of winter in the solar-term calendar, tied to customs such as ancestor offerings, eating nourishing dishes, and preparing for cold in several East Asian countries. In Vietnam, Lập Đông is rarely treated as a major festival; it is used mainly in calendrical reckoning, farming, and date selection.
What is Lap Dong and why does it matter?
Lap Dong is the 19th solar term in the system of 24 solar terms, usually falling around 7 or 8 November on the Gregorian calendar each year. It marks the beginning of winter according to the solar term calendar, which is widely used in China, Vietnam, Japan, Korea and Chinese communities. In the East Asian calendrical system, the 24 solar terms divide the year into climatic segments, serving agriculture, date selection and cultural life.
Lap Dong is not a major holiday in Vietnam like Tet Nguyen Dan or Tet Trung Thu. Its main role is as a calendrical marker: it fixes the moment of seasonal change, affects how lunar months are calculated, influences the choice of auspicious and inauspicious days, and shapes a number of folk customs.
How is Lap Dong formed according to the calendar system?
The system of 24 solar terms is based on the position of the Sun along the ecliptic, divided into 24 equal segments of 15 degrees each. Lap Dong comes before Tieu Tuyet. The book Hiệp kỷ biện phương thư (欽定協紀辨方書, Khâm định edition, Siku Quanshu, 36 volumes) by Yin Lu and colleagues, compiled in 1741, records three phenological signs of Lap Dong: water begins to freeze, the ground begins to harden, and the pheasant dives into the water to become a large clam[1]. This is a phenological record, that is, observation of natural phenomena to mark the solar term.
In the section explaining the eight solar terms, it states that the eight terms are winter solstice, start of spring, spring equinox, start of summer, summer solstice, start of autumn, autumn equinox and start of winter. In the section explaining the eight solar terms, it states that the eight terms are winter solstice, start of spring, spring equinox, start of summer, summer solstice, start of autumn, autumn equinox and start of winter. Lap Dong is classified among the solar terms used to determine the ju in Qi Men Dun Jia, belonging to yang dun or yin dun depending on the system[3].
One point to note: the longitude figures and the way solar terms are assigned to Qi Men ju are conventions of the discipline, not independently measured astronomical data. The timing of a solar term is the calculable part of the calendar, while statements of fortune and misfortune are conventions of the art of date selection.
When does Lap Dong begin in the year?
Lap Dong usually falls on 7 or 8 November on the Gregorian calendar. The exact date shifts slightly from year to year because the Earth's orbit around the Sun does not complete in a whole number of days. The Hiệp kỷ biện phương thư, in its section on the 10th lunar month, lists Lap Dong together with stars and directions such as Thien duc at At, Nguyet duc at Giap, and Nguyet kien at Hoi[4]. This book also records the taboo days around the solar term: one day before Lap Dong is Tu tuyet, and ten days after Lap Dong is Khi vang vong.
The table below summarises the main markers of Lap Dong according to the calendar system:
| Item | Information |
|---|---|
| Order among the 24 solar terms | 19th solar term |
| Solar longitude | 225 degrees |
| Gregorian timing | Around 7 or 8 November |
| Corresponding lunar month | 10th lunar month |
| Previous solar term | Suong Giang |
| Next solar term | Tieu Tuyet |
| Phenological signs (per Hiệp kỷ biện phương thư) | Water begins to freeze, the ground begins to harden, the pheasant dives into the water and becomes a clam |
| Corresponding prenatal hexagram (per Kỳ Môn bảo giám) | Cấn |
What are the folk customs during Lap Dong in East Asian countries?
In China, Lap Dong is tied to the custom of "bu dong" (補冬), that is, eating nourishing dishes such as mutton, beef and herbal soups to prepare for winter. This custom is widespread in the north and in some southern regions, but its extent and the dishes involved vary by locality. The book Tuế thời quảng ký (歲時廣記, Siku Quanshu edition, 4 volumes) by Chen Yuanjing of the Southern Song is a type of book that collects anecdotes about the solar terms of the year, but the surviving Siku Quanshu edition has no separate section on Lap Dong in the surviving excerpt[5].
In Vietnam, Lap Dong is rarely organised as a separate festival. In folk practice, people mainly use this solar term to reckon the farming season, choose days for important work, or simply to know that winter has arrived. Some rural areas have the custom of offering to ancestors at the major solar terms of the year, but Lap Dong is usually not among the terms given separate offerings. Customs such as eating nourishing dishes, repairing the house or sewing warm clothes also appear, but they are not as tightly tied to the day of Lap Dong as in China.
How does Lap Dong affect date selection and the lunar calendar?
In the Vietnamese and Chinese lunar calendars, solar terms are one of the two systems that determine months (the other being the lunar phase). Lunar months are named after the principal solar term, and Lap Dong usually falls within the 10th lunar month. The Hiệp kỷ biện phương thư records the auspicious and inauspicious stars, the directions for setting out, and the activities to avoid in the 10th month, including Lap Dong[4].
In date selection, Lap Dong is used as a marker to determine the days of Tu tuyet (one day before the solar term) and Khi vang vong (ten days after the solar term). These are days held to be unsuitable for major undertakings such as marriage, ground-breaking and burial. However, this is a convention of the date selection discipline, not a scientific fact. The book Vạn sự bất cầu nhân lists auspicious and inauspicious stars by day, but does not devote a separate section to Lap Dong[6].
How may schools and books not agree on Lap Dong?
It should be said clearly: calendrical and divination books are not entirely consistent in how they assign Lap Dong to a ju or a hexagram. The Kỳ Môn bảo giám assigns Lap Dong to the Cấn hexagram according to the prenatal eight trigrams[2], while the Kỳ Môn pháp khiếu assigns Lap Dong to the yin dun group in some systems[3]. The Hiệp kỷ biện phương thư (translated edition) only records the stars and directions, without assigning a hexagram[4]. This difference reflects different traditions within the same discipline, not a contradiction of data.
The assignment of heavenly stems and earthly branches, the monthly indicator and the solar terms is the calculable part of the calendar, while statements of fortune and misfortune are only conventions of the art of date selection. Ancient books such as Tuế thời quảng ký record anecdotes for each solar term, but the surviving Siku Quanshu edition has no Lap Dong section in the excerpt[5].
Nhật Nguyệt's suggestions
If you are interested in Lap Dong because you want to choose a day for important work, remember that rules such as Tu tuyet and Khi vang vong are conventions of the date selection discipline, not absolute prohibitions. You can consult them for reference, but the final decision should rest on practical conditions. If you are interested because you want to understand the lunar calendar, Lap Dong is a good starting point for exploring the system of 24 solar terms, since it is tied to the 10th lunar month and to neighbouring terms such as Suong Giang and Tieu Tuyet.
Frequently asked questions
Is Lap Dong a major holiday in Vietnam?
No. In Vietnam, Lap Dong is mainly a calendrical marker, not a major holiday. Major festivals such as Tet Nguyen Dan, Tet Trung Thu and Tet Doan Ngo are the ones widely celebrated. Lap Dong is usually only used in the calendar, in farming and in date selection.
How long does Lap Dong last?
According to the system of 24 solar terms, each term lasts about 15 days, corresponding to 15 degrees along the ecliptic. Lap Dong begins when the Sun reaches 225 degrees of longitude and ends when it reaches 240 degrees, the moment when Tieu Tuyet begins.
How can I find the exact date of Lap Dong this year?
The date of Lap Dong shifts slightly from year to year, usually falling on 7 or 8 November on the Gregorian calendar. To know exactly, you can consult an astronomical calendar or a perpetual calendar that records the 24 solar terms. Reputable lunar calendar sites usually list the date and time each solar term begins.
