How age is calculated
Age is counted in completed years, then completed months, then remaining days, which is how it is counted in most countries. A person born on 15 June 1995 turns 30 on 15 June 2025; the day before, they are 29 years, 11 months and 30 days old.
Born on 29 February
People born on a leap day have a birthday only every four years on the calendar. In non-leap years the calculator treats 1 March as the birthday, which matches the legal rule in many countries.
Other age systems
Some cultures have counted age differently. In the traditional East Asian system a baby is one year old at birth and everyone gains a year at New Year. This calculator uses the international system based on the date of birth.