Vietnamese age: tuổi mụ and tuổi thực
The same two-count structure as its neighbours — one at birth, a year added at the lunar new year — but on a calendar Vietnam computes for itself, at its own meridian. Usually that comes to the same dates as China's. Seven times a century it does not, and this site now computes both.
Your Vietnamese age, tuổi mụ and can chi
Computed as of 29 September 2026. Where this calendar cannot answer for a date, it says so and gives the reason rather than extrapolating.
| Tuổi mụ — nominal age | 28 One at birth, and a year added at Tết. |
|---|---|
| Tuổi thực — completed age | 26 |
| Lunar date of birth | 25th day of the 11th month, lunar year 1999 Computed from Vietnam’s own lunisolar tables, on the 105°E meridian rather than China’s 120°E. That year the two calendars agreed. |
| Can chi year | Kỷ Mão The year you were born into, which begins at Tết. |
| Next Tết Nguyên Đán | 6 February 2027 — năm Đinh Mùi begins 130 days away. Your tuổi mụ goes up that day. |
See the same birth date in all nine calendars — Gregorian to the second, the other East Asian counts, Hijri, Hebrew, Solar Hijri and the planets.
The two counts
| Count | How it is reckoned | Where it applies |
|---|---|---|
| tuổi mụ (also tuổi ta) — nominal age | One at birth; a year added at Tết rather than on the birthday. | Family and everyday speech, fortune-telling and the can chi, and traditional observances. |
| tuổi thực (also tuổi tây) — completed age | Years completed since birth; increments on the birthday. | Documents, law, school, medicine. |
Tuổi mụ is literally the "midwife age" — the count that reckons a child as already a year into life at birth. Tết Nguyên Đán, the lunar new year, is when it advances, so someone born days before Tết reaches two while still a newborn.
Can chi
A Vietnamese year carries a can chi name: one of ten can (heavenly stems) with one of twelve chi (earthly branches), the same sixty-year cycle used across the region, in Vietnamese — Giáp Thìn, Ất Tỵ, Bính Ngọ. The cycle turns at Tết, not on 1 January.
The animals attached to the branches are not the same everywhere. Vietnam's fourth branch, Mão, is the cat where China's 卯 is the rabbit, and the second is usually given as the buffalo rather than the ox. Because of that, this site prints the can chi name for a Vietnamese birth and no animal at all: naming the wrong animal for someone's own year is exactly the kind of small confident error §14 of this project's brief exists to prevent.
Which calendar produced these numbers
The tabulated Âm lịch Việt Nam dataset published by Hồ Ngọc Đức, ingested rather than recomputed. From 1976 it is the official Vietnamese calendar, computed on the 105°E meridian; for 1975 and earlier it is the historical Vietnamese calendar as reconstructed from Prof. Hoàng Xuân Hãn’s research.
This matters more than it sounds. Vietnam computes its lunar months against the meridian 105° East and China against 120° East, an hour apart, and a new moon that falls close to midnight lands on different days under the two. That moves a month boundary; occasionally it moves the intercalation, and Tết arrives a month away from Chinese Lunar New Year. It happened in 1985, and someone born in Vietnam that February has been an Ox at home and a Rat in every zodiac lookup that assumes the Chinese calendar ever since.
Until August 2026 this site computed Vietnamese ages from the Chinese tables and said so here. That was honest and it was also wrong seven times a century. It is now computed from Vietnam's own — the Tết reference table lists every year the two calendars part company.
Published here for 1901–2099; the dataset itself runs 1800–2199. Outside the published window this site declines to answer rather than extrapolate. For 1968 and 1969 these are the Northern dates: the South was still keeping the Chinese calendar, and Tết fell a day later there.
Source: Hồ Ngọc Đức, Âm lịch Việt Nam, ingested 2026-08-23, published here for 1901–2099. Used by permission for personal, non-commercial use; this site carries no advertising and no monetisation of any kind. Outside the published range this site declines to answer rather than extrapolate.
Prose last reviewed 2026-08-23.
Worked examples
Computed on 29 September 2026 in the Asia/Ho_Chi_Minh zone, at build time, from the Vietnamese tables.
| Birthdate | Vietnamese lunar date | Can chi of birth year | tuổi mụ (nominal age) | tuổi thực (completed age) |
|---|---|---|---|---|
| Born 3 February 2024 — a week before the lunar year turned | 24th day of the 12th month, lunar year 2023 | Quý Mão | 4 | 2 |
| Born 12 February 2024 — the first days of the new lunar year | 3rd day of the 1st month, lunar year 2024 | Giáp Thìn | 3 | 2 |
| Born 9 July 1995 — a birthday well clear of the boundary | 12th day of the 6th month, lunar year 1995 | Ất Hợi | 32 | 31 |
| Born 5 February 1985 — the month Vietnam and China were a year apart | 16th day of the 1st month, lunar year 1985 | Ất Sửu | 42 | 41 |
The first two rows are nine days apart and a year apart in both the can chi and tuổi mụ, which is the whole mechanism in one comparison. The last row is the mechanism the Chinese tables cannot reproduce: Tết 1985 fell on 21 January, so a birth on 5 February was already sixteen days into the year of Ất Sửu — while in China the previous year still had a fortnight to run.
The Tết reference table gives the Vietnamese date for every year from 1901 to 2099, alongside the Chinese one and the difference between them. Between 1968 and 1969, when the North and South kept different calendars, the dates given there are the Northern ones.
For the same structure computed on the Chinese calendar proper, see Chinese age; for the version that turns on 1 January instead, see Korean age.