Age Calculator
Choose the age convention and reference date to calculate age and the next birthday.
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Frequently asked questions
How are the extra months and days worked out?
Calendar-style: years first, then months, then days, borrowing the previous month's actual length whenever the day figure would go negative. Total days lived is counted separately and exactly, not as years × 365.
What happens with a 29 February birthday?
In a non-leap year the next birthday is clamped to the last valid day of that month, 28 February. Both dates are read in UTC, and a birth date later than the target date is rejected rather than shown as a negative age.