Qelunai – Articles https://qelunai.com/en/blog/ Qelunai articles on the Vietnamese lunar calendar, auspicious hours, solar terms, feng shui and customs: plain explanations with sources. en What giờ hoàng đạo (auspicious hours) are and how to read them https://qelunai.com/en/blog/gio-hoang-dao-la-gi/ https://qelunai.com/en/blog/gio-hoang-dao-la-gi/ Thu, 29 Oct 2026 17:00:00 GMT A day has 12 double-hours named after the earthly branches, and the old calendar calls 6 of them hoàng đạo. Here is how they are worked out, how to read them and what to know before using them. Open a page of the lunar calendar and you will often see a line like “Giờ hoàng đạo: Tý, Sửu, Mão, Ngọ, Thân, Dậu”. Many people use it to pick a time to set out on a trip or hold a ceremony. So what are giờ hoàng đạo (auspicious hours), and why do they change from day to day?

A day has 12 hours, not 24

The traditional calendar splits a day and night into 12 time slots. Each lasts about two hours and is named after an earthly branch (địa chi):

  • Tý: 23:00–01:00
  • Sửu: 01:00–03:00
  • Dần: 03:00–05:00
  • Mão: 05:00–07:00
  • Thìn: 07:00–09:00
  • Tỵ: 09:00–11:00
  • Ngọ: 11:00–13:00
  • Mùi: 13:00–15:00
  • Thân: 15:00–17:00
  • Dậu: 17:00–19:00
  • Tuất: 19:00–21:00
  • Hợi: 21:00–23:00

In Vietnam these slots follow Vietnam time (UTC+7), the same way the Vietnamese calendar works out lunar dates. The Tý hour spans midnight. Whether 23:00–24:00 belongs to the Tý hour of the day you are looking at or of the next day depends on the school; there is no single agreed reading.

Lacquer painting of a round dial split into twelve parts, each holding one gold zodiac animal: the rat at the bottom, then clockwise the buffalo, tiger, cat, dragon, snake, the horse at the top, goat, monkey, rooster, dog and pig. The upper half is gold with a sun, the lower half dark red with a crescent moon
The twelve earthly-branch hours laid out like a clock face: Tý (rat, midnight) at the bottom, Ngọ (horse, noon) at the top. Clockwise from Tý: Sửu, Dần, Mão (a cat in Vietnam, not a rabbit), Thìn, Tỵ, Ngọ, Mùi, Thân, Dậu, Tuất, Hợi.

Twelve spirits, six good and six bad

Each slot is given one of 12 “duty spirits” (trực thần), always in this order:

  1. Thanh Long, Green Dragon (hoàng đạo)
  2. Minh Đường, Bright Hall (hoàng đạo)
  3. Thiên Hình, Heavenly Punishment (hắc đạo)
  4. Chu Tước, Vermilion Bird (hắc đạo)
  5. Kim Quỹ, Golden Chest (hoàng đạo)
  6. Kim Đường, also called Bảo Quang (hoàng đạo)
  7. Bạch Hổ, White Tiger (hắc đạo)
  8. Ngọc Đường, Jade Hall (hoàng đạo)
  9. Thiên Lao, Heavenly Prison (hắc đạo)
  10. Huyền Vũ, printed as Nguyên Vũ in some books (hắc đạo)
  11. Tư Mệnh, Life Keeper (hoàng đạo)
  12. Câu Trận (hắc đạo)

Six spirits are called hoàng đạo (“yellow path”), the other six hắc đạo (“black path”). A slot that falls on a hoàng đạo spirit is an auspicious hour. So every day has exactly six hoàng đạo hours and six hắc đạo hours.

A ring of twelve lacquer tiles, six in gold leaf and six in black lacquer edged with vermilion; a red pearl marks the starting tile at the top and a gold arrow points clockwise
The twelve spirits in the order of the list above, starting at the tile under the red pearl (Thanh Long) and going clockwise. Gold tiles are hoàng đạo spirits, black tiles are hắc đạo spirits.

Why does each day differ?

The order of the 12 spirits never changes. What changes is the starting point: which hour Thanh Long falls on. That depends on the earthly branch of the day:

  • Dần or Thân days: Thanh Long is at the Tý hour.
  • Mão or Dậu days: Thanh Long is at the Dần hour.
  • Thìn or Tuất days: Thanh Long is at the Thìn hour.
  • Tỵ or Hợi days: Thanh Long is at the Ngọ hour.
  • Ngọ or Tý days: Thanh Long is at the Thân hour.
  • Mùi or Sửu days: Thanh Long is at the Tuất hour.

From the Thanh Long hour, count on in branch order to get the spirit of every other hour.

Example: on a Tý day, Thanh Long is at the Thân hour. Counting on: Dậu is Minh Đường, Tuất is Thiên Hình, Hợi is Chu Tước, Tý is Kim Quỹ, Sửu is Kim Đường, Dần is Bạch Hổ, Mão is Ngọc Đường, Thìn is Thiên Lao, Tỵ is Huyền Vũ, Ngọ is Tư Mệnh, Mùi is Câu Trận. Keep the six hoàng đạo spirits and you get the auspicious hours of a Tý day: Tý, Sửu, Mão, Ngọ, Thân, Dậu. A Ngọ day gives the same six hours.

Because the day’s branch repeats every 12 days, the list of auspicious hours comes back round every 12 days.

Auspicious days are not auspicious hours

Calendars also mark a day as a “hoàng đạo day” or a “hắc đạo day”. It uses the same table of 12 spirits, but the starting point comes from the lunar month, and the cell to read is the day’s branch. A hắc đạo day still has six auspicious hours, and the other way round.

One thing that easily differs between calendars is which month is used for auspicious days: the lunar month or the solar-term month. Where the two give different answers, the Vietnamese perpetual calendars the Qelunai team checked all follow the lunar month. For example, 08/11/2026 is listed as a Bạch Hổ hắc đạo day by ngaydep.com and xemlicham.com. Whether Chinese calendars or the original books do it differently, we have not verified.

Reading auspicious hours sensibly

Hoàng đạo and hắc đạo are conventions of the traditional calendar. There is no scientific evidence that they decide whether something succeeds or fails. A few suggestions:

  • Treat it as a piece of culture. Many families feel more at ease holding a ceremony at a good hour.
  • Do not let a hắc đạo hour stop you from doing what has to be done now, such as seeing a doctor, dealing with an emergency or signing papers on time.
  • When choosing a time, put practical things first: safety, health, weather, paperwork and everyone’s schedule.

Auspicious hours in Qelunai

In the Qelunai app, the Pick a day tab shows each day’s spirit and its auspicious hours, worked out in Vietnam time right on your phone. You can also check quickly on our auspicious hours today page, no account needed.

Sources

Illustrations drawn by AI.

]]> auspicious hours lunar calendar Rằm and mùng một: why two days each month are special https://qelunai.com/en/blog/ram-va-mung-mot/ https://qelunai.com/en/blog/ram-va-mung-mot/ Wed, 28 Oct 2026 17:00:00 GMT Mùng một is the first day of the lunar month and rằm the fifteenth. Where the two days come from, why the Vietnamese calendar sometimes differs from others, and what the offerings usually include. In many Vietnamese families, two days each month are remembered more than the rest: mùng một (the first) and rằm (the fifteenth). On those days people light incense and put fruit and flowers on the altar, and some families remind each other to visit the pagoda. But where do these two days come from, and why is the Vietnamese calendar sometimes one day off from a neighbour’s?

A lunar month starts when the Moon cannot be seen

The Vietnamese lunar calendar is really a lunisolar calendar. Months follow the Moon, while leap months and month names are anchored to the Sun’s position (the solar terms, tiết khí).

Each lunar month starts on the day of the new moon (điểm Sóc). That is when the Sun, the Moon and the Earth are almost in line and the Moon turns its dark side towards us, so it is nearly invisible. The day containing the new moon is mùng một.

The average time between two new moons is about 29.53 days. Since a month must have a whole number of days, a lunar month has 29 days (a short month) or 30 days (a full month). Which months are short and which are full follows no fixed pattern; it depends on when the real new moons happen.

Lacquer painting: a gold Sun on the left sends rays to the right; on the right is a blue Earth with a thin orbit around it. The Moon is drawn twice on the orbit: between the Sun and the Earth it is dark, with only a bright rim on the Sun’s side; on the far side of the Earth it is a bright full disc
Mùng một (the new moon): the Moon lies between the Sun and the Earth and turns its dark side to us. Rằm: the Moon is on the far side, and the face we see is almost fully lit. Not to scale.

Rằm is the 15th

Rằm is the 15th day of the lunar month. The full moon falls roughly halfway between two new moons, so the night of rằm is usually bright with a nearly round moon. Still, the full moon is worked out from the Moon’s real position, while rằm is just a way of counting days, so the night of rằm and the “fullest moon” night do not always match.

A few rằm days in the year have their own names, such as rằm of the first month or rằm of the seventh month. This article only covers the monthly rằm and mùng một.

Lacquer painting of nine gold moons in a row on black: from left to right a dark moon with only a rim, a crescent lit on the right, the right half lit, a nearly full moon, a full moon in the middle, then the lit part shrinking to the left until a dark moon at the end of the row
One lunar month as seen from Vietnam, left to right: mùng một (no moon visible), the Moon growing lit from the right, the full moon around rằm in the middle, the Moon waning with its left side lit, then mùng một of the next month.

Why the Vietnamese calendar sometimes differs from others

The new moon is an astronomical instant that happens at the same moment all over the Earth. But which date it falls on depends on the time zone. The Vietnamese calendar uses Vietnam time (UTC+7). The Chinese calendar uses UTC+8 and the Korean calendar UTC+9.

If the new moon falls close to midnight, two countries may put mùng một on two different Gregorian dates. An example recorded in the documentation of the open-source library doxuta/amlich: Tết 2027 in Vietnam is on 06/02/2027, while Seollal in Korea is on 07/02/2027. The reason is that the new moon falls at about 22:00–24:00 Vietnam time, which is already the next day in Korea.

So when checking rằm or mùng một, use a calendar worked out in Vietnam time. Printed calendars or apps made for other markets can be a day off in a few months of the year.

What the rằm and mùng một offerings usually include

Customs differ from region to region and family to family. Below is a summary of what the prayer texts (văn khấn) published by VietNamNet, VTC News, Infonet and Báo Quốc tế have in common. Most of them say they follow the book Văn khấn cổ truyền Việt Nam (Traditional Vietnamese Prayers, Văn hoá Thông tin publishing house). We have not been able to read the original book.

Offerings usually named in the prayers: incense, flowers, tea and fruit. The prayer to the spirits also mentions kim ngân (votive paper gold).

Two prayers are commonly used on mùng một and rằm:

  • Prayer to the spirits (văn khấn thần linh): addressed to Hoàng thiên Hậu thổ, Đông thần quân, Thổ địa Long mạch and the spirits that look after the house, asking that the family stay safe.
  • Prayer to the ancestors (văn khấn gia tiên): inviting the ancestors on both sides of the family to witness, asking for good health and harmony in the family.

The sources share one small note worth remembering: if your parents are still alive, the person praying usually says “Tổ khảo, Tổ tỷ” instead of “Hiển khảo, Hiển tỷ” in the prayer to the ancestors.

The shorter version on Báo Quốc tế uses fewer titles, while the versions on VietNamNet, VTC News and Infonet follow the same main outline. None of them is “the only correct version”. If your family has its own way of praying handed down by your grandparents, keep it.

Lacquer painting of a red altar table: on the left a vase of pink lotus, in the middle a bronze incense burner with three burning sticks, in front a teapot and two small cups, on the right a footed plate of bananas, a pomelo and mandarins
The four things every prayer text mentions: incense, flowers, tea and fruit.

A few notes

  • What matters in an offering is sincerity, not how big the tray is. The prayers only mention incense, flowers, tea and fruit.
  • Mùng một and rằm may fall on working days. Many families light incense early in the morning or in the evening.
  • Take care with fire and incense when there are small children in the house.

Following rằm and mùng một in Qelunai

The month view in Qelunai marks mùng một, rằm and the start of each solar term, worked out in Vietnam time right on your phone. When you select a mùng một or rằm day, the Calendar screen shows an extra button that opens the rằm and mùng một prayers so you can read them straight away.

Sources

Illustrations drawn by AI.

]]> full moon day new moon day lunar calendar prayers The 24 solar terms: a solar calendar inside the lunar calendar https://qelunai.com/en/blog/24-tiet-khi/ https://qelunai.com/en/blog/24-tiet-khi/ Tue, 27 Oct 2026 17:00:00 GMT Lập xuân, Đông chí and Thanh minh follow the Sun, not the Moon. What the 24 solar terms are, why Lập xuân rarely falls on Tết, and how the terms decide leap months. Flip through a Vietnamese wall calendar and next to the lunar and solar dates you will often see a small extra line: “Lập đông”, “Tiểu tuyết”, “Đông chí”… These are tiết khí, the solar terms. Many people think solar terms are part of the lunar calendar, but they actually follow the Sun, not the Moon.

Solar terms are measured by the Sun’s position

Over a year, seen from Earth, the Sun travels once around the sky along a path called the ecliptic. That circle is divided into 24 points, each 15° apart. Each time the Sun reaches one of these points, a new solar term begins.

The 0° mark is Xuân phân (Spring Equinox). Every further 15° starts the next term: Thanh minh at 15°, Cốc vũ at 30°, and so on up to Đông chí (Winter Solstice) at 270° and Lập xuân (Start of Spring) at 315°. Each solar term lasts about 15 or 16 days.

Because they follow the Sun, solar terms fall on almost the same Gregorian date every year, shifting by a day at most. That is why Lập xuân is usually on 4 or 5 February.

Lacquer painting of a gold Sun in the centre, ringed by an orbit with 24 evenly spaced dots, four of them red at the top, bottom, left and right; a small Earth sits on the orbit; the corners hold apricot blossom, a lotus, rice ears and a frosted branch
The 24 solar terms are 24 points 15° apart around one year; the four red dots are the March equinox, June solstice, September equinox and December solstice. The picture shows the Earth going round the Sun; seen from the Earth, the Sun goes once round the ecliptic.

The 24 solar terms by season

Each name is a short description of the weather or the farming season:

  • Spring: Lập xuân (start of spring), Vũ thủy (rain water), Kinh trập (insects waking), Xuân phân (mid-spring, day and night nearly equal), Thanh minh (clear and bright), Cốc vũ (rain for the grain).
  • Summer: Lập hạ (start of summer), Tiểu mãn (grain slightly full), Mang chủng (grain in ear), Hạ chí (midsummer, the longest day in the Northern Hemisphere), Tiểu thử (minor heat), Đại thử (major heat).
  • Autumn: Lập thu (start of autumn), Xử thử (end of heat), Bạch lộ (white dew), Thu phân (mid-autumn, day and night nearly equal again), Hàn lộ (cold dew), Sương giáng (frost descends).
  • Winter: Lập đông (start of winter), Tiểu tuyết (minor snow), Đại tuyết (major snow), Đông chí (midwinter, the longest night in the Northern Hemisphere), Tiểu hàn (minor cold), Đại hàn (major cold).

The names reflect the climate where the calendar was born. Weather in different parts of Vietnam can be quite different: the south gets no snow at Tiểu tuyết or Đại tuyết. For farmers, markers like Lập xuân are still the time to get tools and land ready for the new crop.

Four lacquer panels like a folding screen: spring with yellow apricot blossom and a farmer ploughing with a buffalo in drizzle; summer with a lotus pond and young rice under a gold sun; autumn with ripe rice harvested in the mist; winter with frosted branches beside a thatched house
Left to right: spring, summer, autumn, winter. Each season has six solar terms.

Four dates you can check

Xuân phân, Hạ chí, Thu phân and Đông chí are also the four astronomical events that observatories publish. According to U.S. Naval Observatory (USNO) data for 2024, converted to Vietnam time:

Solar term · Moment (Vietnam time)

Xuân phân (Spring Equinox) · 20/3/2024, 10:06

Hạ chí (Summer Solstice) · 21/6/2024, 03:51

Thu phân (Autumn Equinox) · 22/9/2024, 19:44

Đông chí (Winter Solstice) · 21/12/2024, 16:20

This shows that solar terms are not rough conventions: they match real astronomical moments that can be calculated to the minute. Calendar software uses astronomical formulas (such as Jean Meeus’s) to compute the Sun’s longitude and find when each term begins.

Why Lập xuân rarely falls on Tết

Tết Nguyên đán, the Lunar New Year, is the first day of the first lunar month, so it is counted by the Moon. Lập xuân is counted by the Sun. The two are worked out differently, so they have no fixed link, and Lập xuân only now and then lands exactly on the first day of Tết.

This matters in Bát tự (Four Pillars). In Bát tự the new year starts at Lập xuân, not at Tết, and each month also starts at a solar term. So someone born after Tết but before Lập xuân may have a different year stem and branch from their usual “lunar age”.

Solar terms decide the leap month

The lunar calendar needs the solar terms so that it does not drift away from the seasons. Of the 24 terms, the 12 at even multiples of 30° (such as Xuân phân at 0° and Đông chí at 270°) count as principal terms (trung khí). The lunar month that contains Đông chí is month 11.

A lunar month averages about 29.53 days, so 12 lunar months come to only about 354 days, around 11 days short of one trip of the Sun. After a few years there will be a lunar month containing no principal term. Under the rule of the traditional Chinese calendar, which the Vietnamese lunar calendar also uses, that month becomes the leap month. This keeps Tết always at the end of winter and the start of spring.

Solar terms in the Qelunai app

In the Calendar tab of the Qelunai app, the “Coming up” list shows the day each solar term begins, along with the first and fifteenth of each lunar month. Dates are worked out in Vietnam time, so they can differ by a day from calendars printed in other countries. You can also take a quick look on our lunar calendar page.

Next time you see “Lập đông” on a calendar page, you will know the Sun has just reached 225° on the ecliptic.

Sources

Illustrations drawn by AI.

]]> solar terms lunar calendar Start of Spring House direction in Bát Trạch: sitting, facing and the eight good and bad sectors https://qelunai.com/en/blog/huong-nha-bat-trach/ https://qelunai.com/en/blog/huong-nha-bat-trach/ Mon, 26 Oct 2026 17:00:00 GMT Bát Trạch (Eight Mansions) splits a house into eight sectors, four good and four bad, by the side it sits on. How the house type is found, the East and West groups, and common layout tips. When buying or renovating a home, many people are told to “check whether the house direction suits your age”. Most advice of this kind comes from Bát Trạch (Eight Mansions), a school of feng shui that splits a house into eight sectors, four good and four bad. This article explains what Bát Trạch says, keeping strictly to what public sources record. It is cultural knowledge for reference, not a promise of wealth or health.

Sitting and facing: the two sides of a house

Every house has two opposite sides. Facing (hướng) is the way the front looks out. Sitting (tọa) is the back of the house, opposite the facing. A house that faces south sits north.

According to Bát Trạch sources such as Feng Shui Web, Absolutely Feng Shui and Feng Shui Today, a house’s type (“trạch”) is named after its sitting direction, which matches one trigram of the bagua:

Sitting · House type

North · Khảm

South · Ly

East · Chấn

Southeast · Tốn

Northwest · Càn

Southwest · Khôn

Northeast · Cấn

West · Đoài

For example, a house facing south sits north, so it is a Khảm house.

One point often causes confusion: many popular Vietnamese websites talk about the “house direction” (the way the front faces) without saying whether they mean sitting or facing. When you read a lookup table, check whether it uses sitting or facing before comparing.

Lacquer painting of a house with a red tiled roof seen from above, inside a walled yard. The front door and a brick yard with a lotus pot are at the bottom of the picture; a gold arrow points down from the front door, and a red arrow points up from the back of the house. In the top right corner is an eight-pointed compass rose with a red top point
The gold arrow is the facing direction (where the front looks out); the red arrow is the sitting direction (the back of the house). The red point of the compass is north: this house faces south and sits north, so it is a Khảm house.

East group and West group houses

The eight house types fall into two groups:

  • East group (Đông tứ trạch): Khảm, Ly, Chấn, Tốn (sitting north, south, east, southeast).
  • West group (Tây tứ trạch): Càn, Khôn, Cấn, Đoài (sitting northwest, southwest, northeast, west).

People are also split into two groups by their kua number (mệnh quái), worked out from birth year and gender. Kua numbers 1, 3, 4 and 9 belong to the East group; 2, 6, 7 and 8 to the West group. Sources usually advise living in a house of your own group. Even so, Absolutely Feng Shui says plainly that this is “not mandatory”.

Eight sectors: four good, four bad

In each house type, the eight directions around the house are linked to eight stars:

  • Four good sectors: Sinh Khí, Thiên Y, Diên Niên, Phục Vị.
  • Four bad sectors: Họa Hại, Ngũ Quỷ, Lục Sát, Tuyệt Mệnh.

Phục Vị is always on the sitting side itself. For example, for a Khảm house (sitting north), Chinese sources such as the article on Sohu give: Sinh Khí in the southeast, Thiên Y in the east, Diên Niên in the south, Phục Vị in the north; Họa Hại in the west, Ngũ Quỷ in the northeast, Lục Sát in the northwest, Tuyệt Mệnh in the southwest.

The eight-sector table for all eight house types in the Qelunai app has been checked, all 64 cells, against two separate Chinese sources.

Lacquer painting of a round disc split into eight equal sectors around a small roof at the centre; a red triangle at the top edge marks north. Clockwise from the top sector: gold, black, gold, gold, gold, black, black, black
The eight sectors of a Khảm house (sitting north), with north at the top. Gold sectors are good, black sectors are bad.

Clockwise from the top sector (under the red triangle):

  • North: Phục Vị (good)
  • Northeast: Ngũ Quỷ (bad)
  • East: Thiên Y (good)
  • Southeast: Sinh Khí (good)
  • South: Diên Niên (good)
  • Southwest: Tuyệt Mệnh (bad)
  • West: Họa Hại (bad)
  • Northwest: Lục Sát (bad)

What books often suggest for the layout

Below are the suggestions that at least two public sources agree on. Where the sources disagree, both sides are given.

  • Main door: in or facing a good sector, often Sinh Khí first. Some sources use the occupant’s good directions, others the house’s good sectors.
  • Bedroom: in a good sector, with the head of the bed pointing to one of the sleeper’s four good directions. Sources pick different stars (Diên Niên, Thiên Y, Phục Vị…), so there is no single “right star”.
  • Desk: sit facing the good direction of the person at the desk, often Sinh Khí.
  • Altar: in a good sector. Some sources pick Phục Vị only, others allow any of the four good sectors.
  • Kitchen: the common view is “tọa hung hướng cát” (sit in bad, face good): the kitchen sits in a bad sector while the stove opening faces a good direction. But some articles, such as one on CafeLand, call this a misreading and say the kitchen should be in a good sector.
  • Toilet and storage: in a bad sector, leaving the good sectors free.

Using Bát Trạch with a clear head

Bát Trạch is only one school. Others, such as Huyền Không Phi Tinh (Flying Stars), have their own methods and may give different results. A real home also depends on light, air flow, safety and what the whole family needs. If a feng shui suggestion clashes with those, the practical things should come first.

Analysing your home in the Qelunai app

The Home feng shui screen in the Qelunai app lets you pick the way the front of your house faces (or measure it with your phone’s compass), then works out the sitting side and the house type. It shows the eight good and bad sectors on a nine-cell plan of the house, tells you which saved profiles the house suits, and lists the layout tips above. The wording keeps a neutral “books often suggest” tone and only uses rules backed by two or more public sources.

Sources

Illustrations drawn by AI.

]]> feng shui Eight Mansions house direction