Age Calculator

How it works

Age is counted the way people count it: in whole years that tick over on each birthday, then whole months that tick over on the same day of each month, then the days left over. The calculator steps forward from the birth date one year at a time while it has not passed the reference date, then one month at a time, and reports the remainder in days.

If a step lands on a day that month does not have, it uses the last day of that month. Someone born on February 29 has their birthday on February 28 in common years; someone born on the 31st turns a month older on the 30th of a short month.

Total days lived is the plain difference between the two dates, counted in UTC so that daylight-saving changes cannot shift it. The next birthday is the first anniversary strictly after the reference date, so on the birthday itself the next one is a full year away.

The reference date is a fixed input rather than the clock, so the same inputs always give the same answer and the page can be checked by hand. Type today's date in the "Age on" fields to get the current age.

Formula

years  = max n with birth + n years ≤ reference
months = max m (0–11) with birth + years + m months ≤ reference
days   = reference − (birth + years + months)
total days = day number(reference) − day number(birth)
next birthday = birth + (years + 1) years;  days until = next − reference
a step onto a missing day (Feb 29, the 31st) uses the last day of that month

Example

Born June 15, 1990, measured on October 1, 2026: the 36th birthday was June 15, 2026; three months on is September 15; 16 more days reach October 1. Age 36 years, 3 months, 16 days, or 435 months, or 13,257 days. The next birthday is June 15, 2027, 257 days away.

Jeanne Calment, the oldest person on record, was born February 21, 1875 and died August 4, 1997: 122 years, 5 months, 14 days, which is 44,724 days.

Born February 29, 2000, measured on February 28, 2026: the 26th birthday falls on February 28 because 2026 is not a leap year, so the age is exactly 26 years, 0 months, 0 days.

Assumptions and limitations

• Ages are measured in whole calendar days; the time of birth and time zones are ignored.
• A February 29 birthday is observed on February 28 in common years. Some jurisdictions use March 1 for legal purposes; this calculator does not.
• Months are calendar months of varying length, so "3 months" is 89 to 92 days depending on where in the year it falls.
• Dates follow the Gregorian calendar, applied back to the year 1000.

Frequently asked questions