Age calculator
Your birth date is calculated on your device and never sent to any server.
Full years only: if this year's birthday hasn't arrived yet, subtract one year. The traditional Chinese virtual age (虚岁) runs 1–2 years higher; here it uses the simplified rule "current lunar year − birth year + 1".
When to use it
- A form asks for your age in completed years and you only have the date of birth — you need the count that ticks over on the birthday, not on 1 January.
- You want to know how many days and full months you have been alive, or how long until the next birthday, for a countdown or a milestone.
When not to
- You need nominal East Asian age (虚岁): this tool counts completed years only, while nominal age follows the lunar year and can be 1–2 years higher.
- You need an infant's age to the hour, or the birth date involves another time zone: the calculation uses local midnights only, not the time or place of birth.
Your date of birth stays in the browser — it is not uploaded, written into the URL or stored locally, because birth dates are private. Limits: Gregorian dates and local midnights only, with no birth time or time zone; a 29 February birthday counts down to 1 March in common years; lunar birthdays, nominal age and legal periods follow different rules.
Frequently asked
What is the difference between completed age and nominal age?
Completed age (周岁) adds one year only when the birthday arrives; nominal age (虚岁) starts at 1 at birth and adds one at each lunar new year, so it is usually 1–2 years higher. Example: born in December 2025, after the 2026 Spring Festival the nominal age is 2 while the completed age is still 0. This tool reports completed age only; the nominal-age formula in the page note, current lunar year − birth year + 1, is a simplification that is off by one for January–February births where the Gregorian and lunar years differ. Forms, school entry and retirement use completed age; family trees and older relatives usually quote nominal age.
Does the days-alive count include the day I was born?
No. It subtracts two local midnights and divides by 86,400,000 ms, so the birthday is day 0; if you prefer “born day = day 1”, add 1. It is also not age × 365 days: leap years add a day, and the months since the last birthday are not captured. In regions with daylight saving, a transition day is 23 or 25 hours long, so the integer division can be off by one; mainland China has no DST, so it is unaffected.
How is the next birthday calculated for someone born on 29 February?
The tool uses browser dates: a common year has no 29 February, so the date normalises to 1 March and the countdown targets 1 March at 00:00. Legal period rules are separate: Article 202 of China's Civil Code says that when a period counted in months has no corresponding day, the last day of that month applies — 28 February here. Japanese civil law reaches the same end-of-month result. For celebrations, 28 February or 1 March is a family choice; for contracts and deadlines, follow the applicable rule rather than this countdown.