Chinese age: 虚岁 and 周岁
Two counts, and the older of them does not use your birthday at all. 虚岁 starts at one and advances at Lunar New Year, so it changes on a date that moves through late January and February — and so does the zodiac animal people ask about.
The two counts
| Count | How it is reckoned | Where it applies |
|---|---|---|
| 虚岁 (xūsuì) — nominal age | One at birth; a year added at each Lunar New Year, not on the birthday. | Everyday and family speech, traditional medicine, and anything reckoned against the zodiac. Still the first answer many older speakers give. |
| 周岁 (zhōusuì) — full age | Years completed since birth; increments on the birthday. | Identity documents, law, medicine, school — everything official. |
The gap is one or two years and depends on two things rather than one: whether the birthday has passed, and how much of the year has elapsed since Lunar New Year. A baby born in the days before Lunar New Year is 虚岁 2 within a fortnight of being born — the same arithmetic that gives Korean 세는나이 its New Year jump, moved onto a lunar boundary.
The zodiac turns at Lunar New Year
The animal belongs to the lunar year, and the lunar year begins somewhere between 21 January and 21 February. Anyone born in January or the first days of February belongs to the previous year's animal, and lookups that key off the Gregorian year get them wrong. TheLunar New Year reference table gives the exact date for 1901–2099.
The animal is only half of the name. Each year takes one of ten heavenly stems and one of twelve earthly branches; the stem carries the element, the branch carries the animal, and the pair repeats every sixty years — which is why a 60th birthday completes a cycle and returns someone to the stem-branch year they were born in.
Where these dates come from
The Gregorian–Lunar Calendar Conversion Tables published by the Hong Kong Observatory, ingested in full rather than recomputed. The lunar month begins on the day of the new moon at the meridian used for the modern Chinese calendar.
Published for 1901–2099, the range HKO tabulates. Outside it this site declines to answer rather than extrapolate. The Vietnamese and Korean lunisolar calendars use their own meridians and can differ from this one by a day.
Source: Hong Kong Observatory, Gregorian–Lunar Calendar Conversion Table, ingested2026-08-18. This site does not use ICU's built-in Chinese calendar, which places Lunar New Year on the wrong day in 1954, 2027 and 2030 among others.
Prose last reviewed 2026-08-19.
Worked examples
Computed on 20 August 2026 in the Asia/Shanghai zone, at build time, by the same module the calculator uses. The first two births are a week apart and land in different lunar years — different lunar date, different zodiac, and a year between their 虚岁.
| Birthdate | Lunar birth date | Zodiac year of birth | 虚岁 | 周岁 |
|---|---|---|---|---|
| Born 3 February 2024 — a week before Lunar New Year | 24th day of the 12th month, lunar year 2023 | Gui-Mao (Water Rabbit) | 4 | 2 |
| Born 10 February 2024 — Lunar New Year itself | 1st day of the 1st month, lunar year 2024 | Jia-Chen (Wood Dragon) | 3 | 2 |
| Born 31 March 2023 — born inside a leap month | 10th day of the leap 2nd month, lunar year 2023 | Gui-Mao (Water Rabbit) | 4 | 3 |
| Born 20 August 1990 — a birthday well clear of the boundary | 1st day of the 7th month, lunar year 1990 | Geng-Wu (Metal Horse) | 37 | 36 |
The third row is a birth in a leap month. Twelve lunar months fall about eleven days short of a solar year, so roughly every third year repeats a month — a leap second month is a second month 2, not a month 13. A birthday in a leap month has no exact anniversary in most years, which families resolve by convention rather than by rule.
What this site will not tell you
Outside 1901–2099 it declines to answer. The tables end there, and the flat fallback that generated code often uses — assuming Lunar New Year is always around 4 February — misassigns the zodiac for every January birth in the years it covers. A refusal is a smaller error than a wrong animal.
The lunar birth date shown above is the Chinese calendar's. Korea and Vietnam compute their lunisolar months against their own meridians, so a Vietnamese or Korean lunar birthday can differ from this one — see Vietnamese age.