Age is not just a subtraction of years: check whether the birthday has passed
Completed age counts full years already lived. A calculation for a particular date must compare the month and day as well as the year.
Age calculator →Two answers can occur in the same calendar year
Someone born on 2000-10-20 is 25 on 2026-10-19 and turns 26 on 2026-10-20. Subtracting 2000 from 2026 gives the preliminary difference of 26, but it ignores whether that year’s birthday has arrived. This site uses the completed-years convention, so the day before and the birthday itself correctly produce different answers.
Total days are a different output
Dividing days lived by 365 is not a reliable shortcut for completed age because leap days occur inside some intervals. A period spanning February 2024 can include February 29. Total days answer a useful question about elapsed calendar days, but do not replace the anniversary comparison required for completed years.
Check the rule for the intended use
Use an unambiguous year-month-day date rather than a format such as 10/11, which can be read differently by region. School admission, insurance and legal rules may define eligibility differently; this calculator does not certify eligibility. To find age on a future date, enter that date as the end date directly. Keep the intended reference date in the record so the answer is not later mistaken for today’s age.
Try the calculators
- Age calculator
Find completed years and days between dates.
- Date difference
Count calendar days between two dates.
- Add days to date
Find the date before or after a number of days.