Age calculator
An age calculator counts whole years, leftover months, then leftover days from a date of birth to a second date. It is not anyone's real birthday — 1 January 2000 is the example so the page has a readable default. If the end date is before the birth date, the range is invalid.
Calculate age from date of birth
Age calculator FAQ
How are months counted?
Whole calendar months after whole years, then leftover days — not fixed 30-day blocks. Decimal years divide total days by 365.2425, the mean Gregorian year, not a solar-age clock.
Is this anyone’s real date of birth?
No. 1 January 2000 is an example so the page has a readable default. Names you type stay in this browser if you save; they are not sent anywhere.
What if the end date is before the birth date?
That row is invalid. The sidebar follows the first valid person.
When is the next birthday if they were born on 29 February?
In a common year it uses 28 February. Milestone dates add calendar years from the birth date, so 29 February plus 18 years lands on 1 March in a common year.