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Age Calculator

Calculate calendar age between a date of birth and a chosen as-of date, with leap-year and month-boundary handling.

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About This Tool

What it does

Calculates a calendar interval in completed years and months plus remaining days, alongside the exact elapsed-day count between the two Gregorian dates.

Who it's for

Anyone checking age on today’s date or another date. For legal eligibility or official deadlines, confirm the governing jurisdiction’s age rules.

Your privacy

Dates are processed locally in your browser and are not sent to ToolBullet.

Method and sources

Uses strict Gregorian calendar dates in year-month-day order. Leap-year rules follow the U.S. Naval Observatory. A 29 February birthday is treated as 28 February in non-leap years for this calculator’s anniversary and countdown logic; legal conventions can differ. Sources reviewed 23 June 2026: USNO leap-year rules; ISO 8601-1:2019 date representations.

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Frequently Asked Questions

The calculator counts completed years from the birth date, then completed months from that anniversary, then the remaining calendar days. It separately calculates total elapsed days using UTC day numbers so daylight-saving clock changes do not add or remove a day.
Yes. It validates real Gregorian dates, including the century rule: years divisible by 100 are not leap years unless divisible by 400. Month-end anniversaries are clamped to the last valid day of the target month.
For this calculator, the anniversary is treated as 28 February in a non-leap year. Legal age rules can differ by jurisdiction, so do not rely on this convention for a legal deadline without checking the applicable rule.
Total days is the number of complete calendar-day boundaries between the birth date and the selected as-of date. The start date is day zero, so identical dates produce zero elapsed days.
Yes. Choose an as-of date from the birth date through 31 December 9999. Birth years are offered from 1900 through the current year.
It is a general calendar calculation, not legal advice. Statutes and court rules may define birthdays, leap-day cases, cut-off times or inclusive counting differently.
No. The calculation runs in your browser and ToolBullet does not transmit or store the entered dates.
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