Calculate an age in years from a date of birth and a target date.
The calculator compares the calendar years and then checks whether the birthday has occurred in the target year.
This is a calendar calculation. It does not account for time of day or time zones.
Age is normally measured by completed birthdays. A person can be born in one calendar year and still be the same age until the next birthday. A precise age calculation therefore needs the full birth date and the date on which the age is being checked.
If someone was born on May 10, 1995, they turn 30 on May 10, 2025. On May 9, 2025, their completed-birthday age is still 29. This is why simply subtracting birth years can be off by one.
Calendar calculations involve months with different lengths and leap years. For planning appointments, legal documents, eligibility, or other situations with formal rules, use the relevant official definition of age rather than relying only on a general calculator.
For a related calculation involving two calendar dates, see the Date Difference Calculator. It answers elapsed time between dates rather than a person’s birthday-based age.