How to calculate age
Calendar age = selected date − date of birth, expressed as full years, months and remaining days
Worked example. Age at selected date: -20 years.
Example inputs — Date of birth: 1990-06-15; Age at date: 1970-01-01. Starting values are illustrative.
-20 years, -5 months, -14 days
From George Guju, founder of Calculyn · Educational calculator guidance, not professional advice.
How it works
Age is calculated at your selected date using actual calendar years and months, including leap years. Total hours, minutes and seconds are whole calendar days converted into units, not a time-of-birth or daylight-saving calculation.
Assumptions & limitations
- Results are rounded for display.
Formula and assumptions reviewed October 2026 by the Calculyn team. How we build our calculators
Frequently asked questions
How are leap years handled?
Day counts use actual calendar days, so leap years are included.