Traditional Chinese age: understanding xusui
Nominal and completed age
Xusui (虚岁), usually translated as nominal age, is a way of counting the calendar years a person has entered. Under the Chinese New Year convention, a person starts at one at birth and gains a year on the first day of the first lunar month. Individual birthdays do not trigger another increase.
Completed age counts full years since birth. The term zhousui (周岁) refers to a complete year and, in an infant's life, completion of the first year. The comparisons below count completed age at Gregorian birthday anniversaries, independently of whether the family celebrates a lunar birthday.
| Question | Nominal age | Completed Gregorian age |
|---|---|---|
| What is counted? | Chinese calendar years entered, including the birth year | Completed Gregorian birthday anniversaries |
| What is the number at birth? | One | Zero |
| When does it increase? | Chinese New Year | The person's Gregorian birthday |
| Does a leap month add another year? | No | No |
Calculation example
For someone already born, calculate:
Nominal age = current Chinese calendar-year label − birth Chinese calendar-year label + 1.
Here, a year's label is the Gregorian year in which that Chinese New Year began. Before Chinese New Year, use the previous year's label. Chinese New Year's Day, rather than Lichun, the solar term Beginning of Spring, is the boundary in this calculation.
A baby born on 9 February 2024 was born on the final day of the Chinese calendar year that began in 2023. Chinese New Year fell on 10 February 2024, and the next Chinese New Year on 29 January 2025. Applying the rule gives:
| Gregorian date | Event or position in the calendar | Nominal age | Completed Gregorian age |
|---|---|---|---|
| 9 February 2024 | Birth, in the Chinese calendar year beginning in 2023 | 1 | 0 |
| 10 February 2024 | First Chinese New Year after birth | 2 | 0 |
| 29 January 2025 | Second Chinese New Year after birth | 3 | 0 |
| 9 February 2025 | First Gregorian birthday | 3 | 1 |
By 29 January 2025, only 355 days have passed since birth, but the child has entered three Chinese calendar years. This explains how nominal age can reach three before the first Gregorian birthday. Simply adding one to completed age would miss the New Year boundaries that this convention counts.
Family conventions
A date of celebration, an age on an invitation, and an age recorded in a family history need not be calculated the same way. A family could celebrate a lunar anniversary while writing completed age on the invitation. It could also use nominal age for a longevity celebration and keep the Gregorian birth date in its records.
For a family history, record the age with the date on which it applied and the counting convention. An older register's age cannot safely be converted by automatically subtracting one. The original wording and the person's birth date, when known, preserve more information than an unexplained replacement number.
The New Year boundary also matters. A household calculation that increases at 1 January follows a different rule from the Chinese New Year calculation above. A leap month lengthens the Chinese calendar year without introducing another New Year, so it does not produce an additional increase in nominal age.